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| United States Patent |
5,010,279
|
|
Lathom
, et al.
|
April 23, 1991
|
Switched capacitive ballasts for discharge lamps
Abstract
Ballast and starting circuits for controlling current and voltage applied
to an electrical discharge lamp. The ballast circuits use diodes or other
suitable means to divide the AC power into positive and negative currents.
The ballast circuits use positive and negative capacitors which are
charged by the divided AC line current. In some embodiments the positively
charged capacitors are charged during positive portions of alternating
current and discharged during negative portions of the alternating
current. The negatively charged capacitors are charged during negative
portions of the alternating current and discharged during positive
portions. Transistors or other appropriate switching means are used to
controllably conduct current from the positive and negative capacitors to
the lamp in an asynchronous manner. Startup circuits are included for
boosting the voltage applied to the lamp either manually or automatically
upon startup. A startup regular circuit is also shown for controlling
current flow during periods of high current demand such as during startup.
A further embodiment uses a modulated current control for the positive and
negative sides of the ballast circuit to control power flow therethrough
and maintain power dissipation across power discharge switching
transistors at minimal values.
| Inventors:
|
Lathom; Michael S. (4314 Forest Lakes Dr., Del Valle, TX 78617);
Gullixson; Bruce B. (1513 W. Jackson, Spokane, WA 99205);
Sweat; Bruce P. (3015 E. 16th, Spokane, WA 99205)
|
| Appl. No.:
|
167255 |
| Filed:
|
March 11, 1988 |
| Current U.S. Class: |
315/227R; 315/240; 315/241R; 315/243; 315/244; 315/291; 315/307; 315/DIG.7; 363/59; 363/63 |
| Intern'l Class: |
H05B 037/00; H05B 039/00/.41/14 |
| Field of Search: |
315/227 R,240,241 R,242,243,244,DIG. 4,DIG. 7,302,306,307
320/1
363/59,60,61,62,63
|
References Cited
U.S. Patent Documents
| 3443154 | Apr., 1969 | Hoekstra et al. | 315/340.
|
| 3579026 | May., 1971 | Paget | 315/99.
|
| 3591830 | Jul., 1971 | Woolsey | 315/290.
|
| 3643127 | Feb., 1972 | Laupman | 315/101.
|
| 3968400 | Jul., 1976 | Weinreich | 315/209.
|
| 4042856 | Aug., 1977 | Steigerwald | 315/227.
|
| 4132925 | Jan., 1979 | Schmutzer et al. | 315/208.
|
| 4134043 | Jan., 1979 | Nuver | 315/42.
|
| 4167689 | Sep., 1979 | Quirke | 315/206.
|
| 4219872 | Aug., 1980 | Engelmann | 363/126.
|
| 4230971 | Oct., 1980 | Gerhard et al. | 315/307.
|
| 4260932 | Apr., 1981 | Johnson | 315/205.
|
| 4289993 | Sep., 1981 | Harper et al. | 310/311.
|
| 4337417 | Jun., 1982 | Johnson | 315/290.
|
| 4340843 | Jul., 1982 | Anderson | 315/205.
|
| 4366570 | Dec., 1982 | Bees | 372/70.
|
| 4370600 | Jan., 1983 | Zansky | 315/244.
|
| 4398128 | Aug., 1983 | Wollank | 315/DIG.
|
| 4406976 | Sep., 1983 | Wisbey et al. | 315/307.
|
| 4506196 | Mar., 1985 | Bees | 315/241.
|
| 4555647 | Nov., 1985 | Leskovec et al. | 315/179.
|
| 4719390 | Jan., 1988 | Sairanen | 315/DIG.
|
| 4808886 | Feb., 1989 | Lathom et al. | 315/227.
|
| Foreign Patent Documents |
| 2147159A | Feb., 1985 | GB.
| |
Primary Examiner: LaRoche; Eugene R.
Assistant Examiner: Shingleton; Michael B.
Attorney, Agent or Firm: Wells, St. John & Roberts
Parent Case Text
RELATED APPLICATIONS
This is a continuation-in-part of U.S. patent application Ser. No. 769,482,
filed Aug. 26, 1985 now U.S. Pat. No. 4,808,886 and titled "Switched
Capacitive Ballasts for Discharge Lamps."
Claims
What is claimed is:
1. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive current from
said electricity source during said positive potential portions;
negative electrical charge storage means connected to receive current from
said electricity source during said negative potential portions;
at least one positive current modulator for controllably modulating current
discharged from the positive electrical charge storage means for powering
the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
wherein at least one of said current modulators comprises a current flow
rate control means connected to controllably conduct current from a charge
storage means to power said discharge lamp; and modulation control means
for controlling said current flow rate control means; said current flow
rate control means being a current gate controlled by the modulation
control means to conduct pulses of electrical current from the charge
storage means;
at least one positive current switching means connected to receive positive
current from said positive electrical charge storage means and control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current from said negative electrical charge storage means and control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein said pulses are provided at a modulation frequency which is at
least 10 times more frequent than a lamp frequency at which the discharge
lamp operates.
2. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive current from
said electricity source during said positive potential portions;
negative electrical charge storage means connected to receive current from
said electricity source during said negative potential portions;
at least one positive current modulator for controllably modulating current
discharged from the positive electrical charge storage means for powering
the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
wherein at least one of said current modulators comprises a current flow
rate control means connected to controllably conduct current from a charge
storage means to power said discharge lamp; and modulation control means
for controlling said current flow rate control means; said current flow
rate control means being a current gate controlled by the modulation
control means to conduct pulses of electrical current from the charge
storage means;
at least one positive current switching means connected to receive positive
current from said positive electrical charge storage means and control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current from said negative electrical charge storage means and control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein said pulses are provided at a modulation frequency which is more
frequent than a lamp frequency at which the discharge lamp operates.
3. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive current from
said electricity source during said positive potential portions;
negative electrical charge storage means connected to receive current from
said electricity source during said negative potential portions;
at least one positive current modulator for controllably modulating current
discharged from the positive electrical charge storage means for powering
the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current from said positive electrical charge storage means and control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current from said negative electrical charge storage means and control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one current regulator means connected between a current modulator
and the discharge lamp.
4. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising;
positive electrical charge storage means connected to receive current from
said electricity source during said positive potential portions;
negative electrical charge storage means connected to receive current from
said electricity source during said negative potential portions;
at least one positive current modulator for controllably modulating current
discharged from the positive electrical charge storage means for powering
the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current from said positive electrical charge storage means and control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current from said negative electrical charge storage means and control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one current regulator means connected between a current modulator
and the discharge lamp, and at least one peak voltage generator connected
to supply a charge at a voltage which is sufficient to initiate
luminescence of the discharge lamp.
5. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
at least one positive current regulation means connected between said
positive current modulator and the positive current switching means;
at least one negative current regulation means connected between said
negative current modulator and the negative current switching means;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
6. A ballast circuit according to claim 5 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
7. A ballast circuit according to claim 5 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
8. A ballast circuit according to claim 5 wherein at least one of the
current modulators is a pulse width modulator.
9. A ballast circuit according to claim 5 wherein the positive and negative
current modulators are pulse width modulators.
10. A ballast circuit according to claim 5 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
11. A ballast circuit according to claim 5 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
12. A ballast circuit according to claim 5 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during startup conditions.
13. A ballast circuit according to claim 5 wherein at least one of said
current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
14. A ballast circuit according to claim 13 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the charge storage means.
15. A ballast circuit according to claim 14 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
16. A ballast circuit according to claim 14 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
17. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current stored in said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current stored in said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current from the positive energy storage means and to control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current from the negative energy storage means and to control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
at least one positive current regulation means connected between said
positive current modulator and the positive current switching means;
at least one negative current regualtion means connected between said
negative current modulator and the negative current switching means;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
18. A ballast circuit according to claim 17 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
19. A ballast circuit according to claim 17 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
20. A ballast circuit according to claim 17 wherein at least one of the
current modulators is a pulse width modulator.
21. A ballast circuit according to claim 17 wherein the positive and
negative current modulators are pulse width modulators.
22. A ballast circuit according to claim 17 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
23. A ballast circuit according to claim 17 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
24. A ballast circuit according to claim 17 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during startup conditions.
25. A ballast circuit according to claim 17 wherein at least one of said
current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
26. A ballast circuit according to claim 25 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the charge storage means.
27. A ballast circuit according to claim 26 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
28. A ballast circuit according to claim 26 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
29. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
at least one positive current regulation means connected between said
positive current modulator and the discharge lamp;
at least one negative current regulation means connected between said
negative current modulator and the discharge lamp;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
30. A ballast circuit according to claim 29 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
31. A ballast circuit according to claim 29 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
32. A ballast circuit according to claim 29 wherein at least one of the
current modulators is a pulse width modulator.
33. A ballast circuit according to claim 29 wherein the positive and
negative current modulators are pulse width modulators.
34. A ballast circuit according to claim 29 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
35. A ballast circuit according to claim 29 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
36. A ballast circuit according to claim 29 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during startup conditions.
37. A ballast circuit according to claim 29 wherein at least one of said
current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
38. A ballast circuit according to claim 37 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the charge storage means.
39. A ballast circuit according to claim 38 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
40. A ballast circuit according to claim 38 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
41. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one current regulator means connected between a current modulator
and the discharge lamp.
42. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one positive current regulator means connected between said
positive current modulator and the discharge lamp, and at least one
negative current regulator means connected between said negative current
modulator and the discharge lamp.
43. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one current regulator means connected between a current modulator
and a current switching means.
44. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one positive current regulator means connected between said
positive current modulator and the positive current switching means, and
at least one negative current regulator means connected between said
negative current modulator and the negative current switching means.
45. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of the current modulators operates at a modulation
frequency greater than a lamp operating frequency.
46. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of the current modulators operates at a modulation
frequency which is at least 10 times more frequent than a lamp operating
frequency.
47. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
at least one current regulator means connected between a current modulator
and the discharge lamp, and at least one peak voltage generator connected
to supply a charge at a voltage which is sufficient to initiate
luminescence of the discharge lamp.
48. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein the positive and negative current modulators operate to modulate
positive and negative current as functions related to approximate voltage
drops across the positive and negative current switching means,
respectively.
49. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of said current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means;
wherein the current flow rate control means is a current gate controlled by
the modulation control means to conduct pulses of electrical current from
the charge storage means;
wherein at least one of the current modulators operates at a modulation
frequency greater than a lamp operating frequency at which the positive
and negative current switching means switch.
50. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical charge storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical charge storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical charge storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical charge storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current modulated by said positive current modulator and control positive
current flow through said discharge lamp to define positive lamp discharge
periods;
at least one negative current switching means connected to receive negative
current modulated by said negative current modulator and control negative
current flow through said discharge lamp to define negative lamp discharge
periods;
switching control means for controlling said positive and negative current
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of said current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means;
wherein the current flow rate control means is a current gate controlled by
the modulation control means to conduct pulses of electrical current from
the charge storage means;
wherein at least one of the current modulators operates at a modulation
frequency which is at least 10 times more frequent than a lamp operating
frequency at which the positive and negative current switching means
switch.
51. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged from the positive electrical energy storage
means for powering the discharge lamp;
at least one negative current modulator for controllably modulating current
discharged from the negative electrical energy storage means for powering
the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
at least one positive current regulation means connected between said
positive current modulator and the positive current switching means;
at least one negative current regulation means connected between said
negative current modulator and the negative current switching means;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
52. A ballast circuit according to claim 51 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
53. A ballast circuit according to claim 51 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
54. A ballast circuit according to claim 51 wherein at least one of the
current modulators is a pulse width modulator.
55. A ballast circuit according to claim 51 wherein the positive and
negative current modulators are pulse width modulators.
56. A ballast circuit according to claim 51 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
57. A ballast circuit according to claim 51 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
58. A ballast circuit according to claim 51 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during startup conditions.
59. A ballast circuit according to claim 51 wherein at least one of said
current modulators comprises:
a current flow rate control means connected to controllably conduct current
from an energy storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
60. A ballast circuit according to claim 59 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the energy storage means.
61. A ballast circuit according to claim 60 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
62. A ballast circuit according to claim 60 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
63. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
at least one positive current regulation means connected between said
positive current modulator and the positive current switching means;
at least one negative current regulation means connected between said
negative current modulator and the negative current switching means;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
64. A ballast circuit according to claim 63 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
65. A ballast circuit according to claim 63 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
66. A ballast circuit according to claim 63 wherein at least one of the
current modulators is a pulse width modulator.
67. A ballast circuit according to claim 63 wherein the positive and
negative current modulators are pulse width modulators.
68. A ballast circuit according to claim 63 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
69. A ballast circuit according to claim 63 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
70. A ballast circuit according to claim 63 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during starup conditions.
71. A ballast circuit according to claim 63 wherein at least one of said
current modulators comprises:
A current flow rate control means connected to controllably conduct current
from an energy storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
72. A ballast circuit according to claim 71 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the energy storage means.
73. A ballast circuit according to claim 72 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
74. A ballast circuit according to claim 72 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
75. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
at least one positive current regulation means connected between said
positive current modulator and the discharge lamp;
at least one negative current regulation means connected between said
negative current modulator and the discharge lamp;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods.
76. A ballast circuit according to claim 75 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency.
77. A ballast circuit according to claim 75 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency.
78. A ballast circuit according to claim 75 wherein at least one of the
current modulators is a pulse width modulator.
79. A ballast circuit according to claim 75 wherein the positive and
negative current modulators are pulse width modulators.
80. A ballast circuit according to claim 75 wherein the positive and
negative current modulators operate to modulate positive and negative
current as functions related to approximate voltage drops across the
positive and negative current switching means, respectively.
81. A ballast circuit according to claim 75 and further comprising at least
one peak voltage generator for providing a peak voltage for initiating
substantial electrical discharge within the discharge lamp during startup
conditions.
82. A ballast circuit according to claim 75 and further comprising positive
and negative peak voltage generators for providing positive and negative
charges at positive and negative peak voltages for initiating substantial
electrical discharge within the discharge lamp during the positive and
negative lamp discharge periods, respectively, during startup conditions.
83. A ballast circuit according to claim 75 wherein at least one of said
current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means.
84. A ballast circuit according to claim 83 wherein the current flow rate
control means is a current gate controlled by the modulation control means
to conduct pulses of electrical current from the charge storage means.
85. A ballast circuit according to claim 84 wherein at least one of the
current modulators operates at a modulation frequency greater than a lamp
operating frequency at which the positive and negative current switching
means switch.
86. A ballast circuit according to claim 84 wherein at least one of the
current modulators operates at a modulation frequency which is at least 10
times more frequent than a lamp operating frequency at which the positive
and negative current switching means switch.
87. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of the current modulators operates at a modulation
frequency greater than a lamp operating frequency.
88. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of the current modulators operates at a modulation
frequency which is at least 10 times more frequent than a lamp operating
frequency.
89. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricty source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein the positive and negative current modulators operate to modulate
positive and negative current as functions related to approximate voltage
drops across the positive and negative current switching means,
respectively.
90. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of said current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means;
wherein the current flow rate control means is a current gate controlled by
the modulation control means to conduct pulses of electrical current from
the charge storage means;
wherein at least one of the current modulators operates at a modulation
frequency greater than a lamp operating frequency at which the positive
and negative current switching means switch.
91. A ballast circuit for controlling electrical current flow through an
electrical discharge lamp from an electricity source providing alternating
electrical current having positive potential portions and negative
potential portions, comprising:
positive electrical energy storage means connected to receive positive
current from said electricity source during said positive potential
portions;
negative electrical energy storage means connected to receive negative
current from said electricity source during said negative potential
portions;
at least one positive current modulator for controllably modulating
positive current discharged through the discharge lamp;
at least one negative current modulator for controllably modulating
negative current discharged through the discharge lamp;
at least one positive current switching means connected to receive positive
current stored in the positive energy storage means and to control
positive current flow through said discharge lamp to define positive lamp
discharge periods;
at least one negative current switching means connected to receive negative
current stored in the negative energy storage means and to control
negative current flow through said discharge lamp to define negative lamp
discharge periods;
switching control means for controlling said positive and negative
switching means so that positive lamp discharge periods do not occur
simultaneously with negative lamp discharge periods;
wherein at least one of said current modulators comprises:
a current flow rate control means connected to controllably conduct current
from a charge storage means to power said discharge lamp;
modulation control means for controlling said current flow rate control
means;
wherein the current flow rate control means is a current gate controlled by
the modulation control means to conduct pulses of electrical current from
the charge storage means;
wherein at least one of the current modulators operates at a modulation
frequency which is at least 10 times more frequent than a lamp operating
frequency at which the positive and negative current switching means
switch.
92. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
charging at least one positive charge storage means during said positive
potential portions;
charging at least one negative charge storage means during said negative
potential portions;
modulating the flow of positive current from the positive charge storage
means;
modulating the flow of negative current from the negative charge storage
means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is more frequent than a lamp operating
frequency at which the discharge lamp operates.
93. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
charging at least one positive charge storage means during said positive
potential portions;
charging at least one negative charge storage means during said negative
potential portions;
modulating the flow of positive current from the positive charge storage
means;
modulating the flow of negative current from the negative charge storage
means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is at least 10 times more frequent than a lamp
operating frequency at which the discharge lamp operates.
94. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
charging at least one positive charge storage means during said positive
potential portions;
charging at least one negative charge storage means during said negative
potential portions;
modulating the flow of positive current from the positive charge storage
means;
modulating the flow of negative current from the negative charge storage
means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
regulating at least one of the positive or negative currents after said
modulating steps.
95. A method according to claim 94 wherein at least one of said modulating
steps is accomplished at a modulation frequency which is more frequent
than a lamp operating frequency at which the discharge lamp operates.
96. A method according to claim 94 wherein at least one of said modulating
steps is accomplished at a modulation frequency which is at least 10 times
more frequent than a lamp operating frequency at which the discharge lamp
operates.
97. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
storing positive electrical energy in at least one first positive
electrical energy storage means during said positive potential portions;
storing negative electrical energy in at least one first negative
electrical energy storage means during said negative potential portions;
modulating a main operating flow of positive current from the positive
charge storage means;
modulating a main operating flow of negative current from the negative
charge storage means;
storing modulated positive electrical energy in at least one second
positive electrical energy storage means;
storing modulated negative electrical energy in at least one second
negative electrical energy storage means;
controllably conducting modulated positive current from the at least one
second positive electrical energy storage means to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current from the at least one
second negative electrical energy storage means to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is more frequent than a lamp operating
frequency at which the discharge lamp operates.
98. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
storing positive electrical energy in at least one first positive
electrical energy storage means during said positive potential portions;
storing negative electrical energy in at least one first negative
electrical energy storage means during said negative potential portions;
modulating a main operating flow of positive current from the positive
charge storage means;
modulating a main operating flow of negative current from the negative
charge storage means;
storing modulated positive electrical energy in at least one second
positive electrical energy storage means;
storing modulated negative electrical energy in at least one second
negative electrical energy storage means;
controllably conducting modulated positive current from the at least one
second positive electrical energy storage means to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current from the at least one
second negative electrical energy storage means to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is at least 10 times more frequent than a lamp
operating frequency at which the discharge lamp operates.
99. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
storing positive electrical energy in at least one positive electrical
energy storage means during said positive potential portions;
storing negative electrical energy in at least one negative electrical
energy storage means during said negative potential portions;
modulating a main operating flow of positive current from the positive
charge storage means;
modulating a main operating flow of negative current from the negative
charge storage means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is more frequent than a lamp operating
frequency at which the discharge lamp operates.
100. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
storing positive electrical energy in at least one positive electrical
energy storage means during said positive potential portions;
storing negative electrical energy in at least one negative electrical
energy storage means during said negative potential portions;
modulating a main operating flow of positive current from the positive
charge storage means;
modulating a main operating flow of negative current from the negative
charge storage means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
wherein at least one of said modulating steps is accomplished at a
modulation frequency which is at least 10 times more frequent than a lamp
operating frequency at which the discharge lamp operates.
101. A method for controlling current flow through an electrical discharge
lamp powered by an electricity source providing alternating electrical
current having positive potential portions and negative potential
portions, comprising:
storing positive electrical energy in at least one positive electrical
energy storage means during said positive potential portions;
storing negative electrical energy in at least one negative electrical
energy storage means during said negative potential portions;
modulating a main operating flow of positive current from the positive
charge storage means;
modulating a main operating flow of negative current from the negative
charge storage means;
controllably conducting modulated positive current to the discharge lamp to
define positive lamp discharge periods;
controllably conducting modulated negative current to the discharge lamp to
define negative lamp discharge periods;
controlling the lamp discharge periods so that the negative lamp discharge
periods do not occur simultaneously with the positive lamp discharge
periods;
regulating at least one of the positive or negative currents after said
modulating steps.
102. A method according to claim 101 wherein at least one of said
modulating steps is accomplished at a modulation frequency which is more
frequent than a lamp operating frequency at which the discharge lamp
operates.
103. A method according to claim 101 wherein at least one of said
modulating steps is accomplished at a modulation frequency which is at
least 10 times more frequent than a lamp operating frequency at which the
discharge lamp operates.
Description
TECHNICAL FIELD
The technical field of this invention is ballast circuits for controlling
current flow through electrical discharge lamps.
BACKGROUND OF THE INVENTION
Electrical discharge lamps are widely used in various forms, such as
fluorescent lights, neon lights, mercury vapor lights and sodium vapor
lights. These and many other types of electrical discharge lamps are known
and possible using technology which began in the 1800's when many
scientists experimented with electrical discharge lamps.
Electrical discharge lamps are characterized by an envelope of glass or
other transparent material which encloses a volume of appropriate gas. The
enclosed gas can be of a variety of types and combinations which are
capable of being ionized to allow electrical current to flow therethrough.
Examples of suitable gases employed in electrical discharge lamps include
air, neon and argon. These gases are often combined with small quantities
of suitable metals and other materials which improve the ionization or
light emissive properties of the lamp. Examples of metals commonly used in
discharge lamps are sodium and mercury, which vaporize as a result of the
heat generated by the lamps. Discharge lamps are also manufactured using
combinations of gases such as neon and argon with metal halides such as
mercury iodide and sodium iodide.
The variety of gases and added materials used in discharge lamps have
widely varying voltage requirements for initiating ionization. The voltage
or potential required across the electrodes before ionization will occur
depends upon the gas type, internal pressure of the gas, gas temperature,
and electrode spacing. After the gas within a discharge lamp becomes
ionized, current flows more readily because of the increased number and
density of available charge carriers. The increased number of charge
carriers greatly reduces the resistance across the electrodes as compared
to the starting resistance required when initiating ionization. This
decrease in the electrical resistance across the lamp electrodes requires
that some form of current limiting device be used in conjunction with the
discharge lamp to control the flow of current and prevent the destructive
amounts of heat which would be caused thereby. Current control is also
desired to reduce power consumption and optimize the illumination output
of the lamp. This current limiting function for discharge lamps has
typically been performed by an electrical device termed a ballast.
Prior art discharge lamp ballasts have typically used a transformer or
other induction coil between the source of electricity and the discharge
lamp in order to limit current flow through the lamp. Such transformer
ballasts have also often been used to boost the starting voltage to the
lamp. Such prior art inductive ballasts suffer from a number of
disadvantages. Transformers are relatively costly to manufacture and are
also relatively large and heavy. This increases the total cost of the
discharge lamp and further requires that relatively strong standards,
poles, overhanging arms and other supporting structures be employed.
Increased size and strength for foundations and other structural members
must also accordingly be provided.
It has also not been practical to remotely mount transformer ballasts at
the base of a light pole or otherwise in a remote location because of the
relatively high starting or ionization voltage required. Supplying such
starting potential has been difficult or impossible to attain when lengths
of wire greater than 25-30 feet have been used because of line losses and
voltage decreases occurring due to capacitance developed across the supply
wiring. Accordingly, it has been standard practice to mount the heavy,
bulky transformers immediately adjacent the lamp.
The close mounting of inductive ballasts to discharge lamps typically
causes very significant increases in installation and maintenance costs.
Installation costs are increased because of the increased size and
structural capability which must be provided in any light fixture and
supporting structure. Placement of such heavy ballasts in street lighting
and other applications also usually entail an overhanging configuration in
the added weight of the ballasts which further increase the demands placed
upon the supporting poles and other structural elements. Since these poles
and other supporting structures are often tall, slender, and free
standing, the incremental weight of the inductive ballasts require a
disproportionately large amount of the installation costs. Further
aggravating these basic structural problems are the effects of wind upon
light standards. The large size of the ballasts and associated hoods are
more easily displaced by wind forces striking the units atop typically
slender light standards, thus displacing the load further off center and
intensifying the structural loading problem associated with the weight of
the ballasts.
Inductive ballasts must also be shielded from the wind and weather thus
requiring additional expense for protective hoods or other coverings. Such
protective hoods are relatively large thus increasing the wind loading and
weight placed upon the structure which still further increases the costs
of manufacturing and installation.
The installation costs of discharge lamp lighting is further increased when
transformer ballasts are used because of the relatively high costs of
crating, shipping and handling the heavy and bulky transformer.
Manufacture of such transformer ballasts also requires relatively large
scale heavy industry in order to produce economically. The materials and
costs of constructing inductive ballasts are accordingly high.
Maintenance of transformer ballasts has also proven to be costly and
difficult. Transformer ballasts produce substantial amounts of heat which
tend to deteriorate the coil winding insulation thus leading to short
circuiting of the coils and replacement of the ballast. Since the
transformer ballasts cannot be conveniently mounted in remote locations
from the lamp, this often requires cranes in order to remove and replace
deficient ballasts. This accordingly increases maintenance costs.
Vibration produced by transformer ballasts may also cause fluctuating or
cyclical loading on the light fixture supporting structures which requires
increased strength, or in some cases premature failure, resulting damage
and maintenance costs. The expected service life of transformer ballasts
is also sufficiently short for the above and other reasons so that
maintenance must be performed on a regular basis where numerous units are
in service.
Prior art transformer ballasts also suffer from a tendency to vibrate at 60
Hz and several upper harmonies thereof thus producing very noticeable and
often irritating noise. This noise has restricted most types of discharge
lamps to exterior uses only. Fluorescent type discharge lamps are widely
used in interior applications because they do not produce as much noise as
other more efficient types of discharge lamps which are noisier.
Considering the widespread use of fluorescent lamps, this results in
tremendous increased power costs for using fluorescent type lamps versus
sodium vapor and other more efficient lamps.
Prior art inductive ballasts are also disadvantageous in providing an
inductive power factor component. Power companies typically experience
excess inductive as compared to capacitive reactive power factor
components, thus requiring installation of power factor correcting
equipment such as large banks of capacitors. Such equipment is expensive
and accordingly increases the cost of power to the consumer. Thus there is
a need for discharge lamp ballasts which produce a capacitive power factor
which can be used to offset power consumed by inductive devices such as
electric motors.
SUMMARY OF THE INVENTION
A preferred form of the invention includes two capacitors or capacitor
banks which are each connected to an incoming alternating current supply
using blocking diodes or some other suitable means for dividing the
positive and negative portions of the alternating current. One capacitor
bank receives the positive portion of the alternating current and the
other capacitor receives the negative portion. Switching means such as
switching transistors are connected between the capacitors and the
discharge lamp being powered in order to control the discharge of positive
and negative operating current through the lamp. The switching means are
asynchronously and alternately opened and closed, thereby alternately
disconnecting and connecting the capacitors in order to discharge the
capacitors through the lamp and provide power thereto.
In some embodiments the switching means are controlled by a suitable
switching control circuit which places the power discharge switches into
an open mode during the associated positive or negative portions used to
charge that respective capacitor. The positive and negative power
discharge switches are placed into a closed mode out of phase with the
positive or negative portions of the AC line cycle which that particular
capacitor receives, thus isolating the lamp from direct discharge of line
current. Current through the lamp is thus controlled by the capacitance of
each capacitor bank and the extent to which they can be discharged during
the period its associated switching means is closed.
Embodiments having manual and automatic starting circuits are also provided
to boost voltage during startup. Preferred embodiments also include
indicator lamps for improved diagnostic maintenance. Still further
circuitry can be provided to regulate power flow to the main capacitors
and through the power discharge switching transistors to thus prevent
excessive current loading during startup. Still further embodiments are
provided with multiple voltage and wattage capabilities using alternate
jumper connectors.
Further embodiments of the invention utilize two or more capacitors or
other electrical energy storage means which are connected to an incoming
alternating current supply using diodes or other suitable means for
dividing the positive and negative portions of the alternating current.
One of the capacitors receives the positive portions of the alternating
current and the other capacitor receives the negative portions. Energy
stored in the positive and negative capacitors or other energy storage
means are controllably conducted to respective positive and negative power
discharge switching means using a controllable positive and negative
modulation circuitry. The positive and negative modulation circuits each
advantageously include modulation transistors which are controlled to
conduct current using suitable modulation driver circuitry. In the
preferred embodiments the modulation circuitry provides pulsed emissions
of operating current thereby minimizing the power dissipation which occurs
in the modulation switching device. The pulsed positive and negative
currents from the positive and negative modulation circuitry is preferably
passed through a suitable filter to eliminate the pulsed nature of the
current emitted therefrom. This is advantageously accomplished using an
inductive choke and associated capacitance. The outputs from the positive
and negative filters are controllably conducted by the positive and
negative power discharge switching means. The lamp power discharge
switching means which control power flow through the discharge lamp and
are operated in an alternating asynchronous manner to conduct positive
current through the lamp during positive lamp discharge portions, and
negative current through the lamp during negative lamp discharge portions.
Preferred circuits according to this invention can also preferably include
arc initiation subcircuits which provide boosted operating voltages for
brief portions of the lamp alternating current cycle for both the positive
and negative currents passed therethrough. The relatively higher voltage
arc initiation discharge allows more efficient operation of the lamp by
initiating discharge with a relatively small amount of higher voltage
current.
One preferred type of current modulation circuit effectively senses the
voltage drop which occurs across the power discharge switching transistors
in order to reduce or minimize the power dissipated across these switches
during operation.
Benefits of the invention can include lower power loss, physical lightness,
reduced noise and interference, compactness, remotely locatable, low heat
output, lower cost mounting structures, less expensive to manufacture,
lower freight costs, capacitive power factor, and better regulation of
current to the needs of the lamp. Some or all of these, and other benefits
of the invention which may be recognized below or in the future, may be
accomplished using ballast circuits according to this invention. Exemplary
preferred forms of the invention will be described below.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the accompanying
drawings.
FIG. 1 is a block diagram showing the principal functional elements of
basic forms of the invention.
FIG. 2 is a schematic circuit diagram of a portion of a preferred circuit
according to this invention.
FIG. 3 is a schematic circuit diagram of a further portion of the preferred
embodiment shown in FIG. 2.
FIG. 4 is a schematic circuit diagram of a further portion of the preferred
embodiment shown in FIGS. 2 and 3.
FIG. 5 is a schematic circuit diagram of an alternative embodiment to the
portion shown in FIG. 2.
FIG. 6 is a schematic circuit diagram of an alternative ballast and
starting circuit according to this invention.
FIG. 7 is a schematic circuit diagram of a further embodiment of the
invention.
FIG. 8 is a schematic circuit diagram of a current regulating circuit
useful with the embodiment shown in FIGS. 2, 3 and 4.
FIG. 9 is a block diagram showing principal functional elements of an
alternative form of the invention.
FIG. 10 is a schematic circuit diagram showing a portion of a preferred
circuit according to the embodiment of FIG. 9.
FIG. 11 is a schematic circuit diagram showing a further portion of the
preferred embodiment showing FIG. 10.
FIGS. 12A and 12B are schematic circuit diagrams showing further portions
of the alternative embodiment partially shown in FIGS. 10 and 11. The
portions shown in FIGS. 12A and 12B represent the modulator drive
circuitry for the positive side of the electronic ballast.
FIGS. 13A and 13B are schematic circuit diagrams showing further portions
of the preferred embodiment shown in FIGS. 10, 11, 12A and 12B. The
portions shown in FIGS. 13A and 13B represent the modulator drive
circuitry for the negative side of the electronic ballast.
FIG. 14 is a graph showing voltage across a discharge lamp operated using
the circuitry of FIGS. 9-13B.
FIG. 15 is a graph showing current conducted through a discharge lamp
operated using the circuitry of FIGS. 9-13B.
FIG. 16 is a graph showing voltage between the supply side of a discharge
lamp and the base of the positive power discharge transistors shown in the
circuitry of FIGS. 9-13B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In compliance with the constitutional purpose of the Patent Laws "to
promote the progress of science and useful arts" (Article 1, Section 8),
applicant submits the following disclosure of the invention.
FIG. 1 shows a basic conceptual model of the fundamental functional
elements of many of the preferred embodiments of this invention. An
alternating current power supply 10 provides power to a switching control
circuit 12 and to a suitable circuit 14 for dividing the alternating
current into separate positive and negative current flows. The negative
and positive current flows are separately supplied to negative and
positive capacitors 16 and 18, respectively. Positive capacitor 18 is
charged during positive portions of the alternating current. Negative
capacitor 16 is charged during negative portions of the alternating
current. Each capacitor is charged directly out of phase with the other in
an alternating manner.
Negative capacitor 16 is controllably discharged through negative switching
transistor 20 to lamp 25 during positive portions of the alternating
current, while positive capacitor 18 is charged. Positive capacitor 18 is
controllably discharged through positive switching transistor 22 to lamp
25 during negative portions of the alternating current, while negative
capacitor 16 is being charged. The capacitors 16 and 18 are thus
alternately charged and then discharged through lamp 25 in a substantially
complementary and asynchronous manner.
FIG. 1 also shows a starting circuit 30 which is used to boost the voltage
applied through either or both positive or negative switching means 22 and
20, respectively. Starting circuit 30 is preferably used for a relatively
short period of time during and immediately after initially supplying
current from power supply 10 to starting circuit 30 and lamp 25.
FIG. 2 shows a portion of a ballast and starting circuit 100 useful in
powering a metal halide electrical discharge lamp 32 such as a 400 watt
sodium iodide lamp. Power is supplied by an alternating current power
supply 34, such as a nominal 120 volt, 60 Hz line current used widely in
the U.S. Power supply 34 is advantageously connected with terminal 35 as
neutral and terminal 36 as the hot terminal at which voltage swings from
approximately -170 volts to +170 volts in a typical 120 volt rms
sinusoidal cycle. The period during which the potential of terminal 36 is
positive with respect to terminal 35 is termed the positive potential
portion. The period during which the potential of terminal 36 is negative
with respect to terminal 35 is termed the negative potential portion.
Together one positive and one negative potential portions essentially
comprise a single alternating current cycle.
Letter A designates a connection of the line voltage to control portions of
the circuit shown in FIG. 4. A fusible surge resistor FR1 is
advantageously provided between line voltage and remaining components of
circuit 100. A thermal circuit breaker, fuse or cutout 40 can
advantageously be included between terminal 35 and terminal B of
transformer 42 of FIG. 3.
The alternating current (a-c) output from fusible resistor FR1 is supplied
to two blocking diodes D1 and D2. Blocking diode D1 is oriented with anode
toward line voltage in order to pass positive current to one side of
capacitor C1. Diode D2 is oppositely oriented to pass negative current to
one side of capacitor C2. The configuration of diodes D1 and D2 thus
divides the alternating current from supply 34 into a positive component
going to capacitor C1 and a negative component going to capacitor C2.
Capacitors C1 and C2 can be any suitable electrical energy storage means.
It has been found preferable not to use electrolytic capacitors. The
opposite sides of capacitors C1 and C2 are connected to neutral terminal
35 which is also connected to terminal 50 of lamp 32.
The positively charged side of capacitor C1 is connected to a first
electrical switching means such as switching transistors Q1 connected in
parallel. Switching transistors Q1 are placed in a closed or conductive
mode by applying a positive emitter to base bias voltage. Base voltage for
switching transistors Q1 is provided by connecting to a positive switching
control circuit 65 at conductor E of FIG. 3.
Switching transistors Q1 are controlled by switching control circuit 65 so
as to only be biased into a closed mode during negative portions of the
alternating current power supplied by current supply 34. This assures that
there is no direct application of line current to lamp 32 through
switching transistors Q1. This arrangement allows current flow to lamp 32
to be limited to the available charge on capacitor C1 during any
particular negative portion of the alternating current cycle.
Resistors R1 are provided between the emitters of transistors Q1 and
conductor 52 to provide an appropriate potential drop between the emitters
of Q1 and conductor 52. Diodes D3 and D4 are provided in series between
the bases of transistors Q1 and conductor 52 in order to protect against
excessive emitter to base biasing voltage and allow flow of current from
conductor E to conductor F as generated by switching control circuit 65.
The negatively charged side of negative capacitor C2 is connected to lamp
32 through a second electrical switching means such as switching
transistors Q2 connected in parallel. Switching transistors Q2 are placed
in a closed or conductive mode by applying a positive emitter to base bias
voltage. Base voltage for switching transistors Q2 is provided by
connecting to conductor G of FIG. 3.
Switching transistors Q2 are only biased into a closed mode during positive
portions of the alternating current power supply so that there is no
direct application of line current to switching transistors Q2. This
arrangement allows current flow to lamp 32 to be limited to the available
negative charge on capacitor C2 during any particular positive portion of
the alternating current cycle because of the blocking action of diode D2
to positive current flow. Additional starting voltage is, however,
provided by starting circuit 31 as will be explained below.
Resistors R2 are provided between the emitters of transistors Q2 and
conductor 60 in order to provide an appropriate potential drop
therebetween. Negative charge from capacitor C2 passes through blocking
diodes D5 and D6 which are used in the starting subcircuit explained
below. Diodes D7 and D8 are provided in series between the base of
transistors Q2 and conductor 60 to prevent excessive biasing voltage and
to allow current flow in switching control circuit 66 of FIG. 3.
An induction coil or choke L1 is advantageously provided between conductor
52 and lamp 32 to help regulate current flow through the lamp and filter
voltage spikes in the power provided from switching transistors Q1 and Q2,
since switching of transistors Q1 and Q2 causes voltage spikes to occur.
FIG. 3 shows a preferred switching control circuit 64 for providing control
signals which control the asynchronous operation of switching means Q1 and
Q2. Switching control circuit 64 can be any one of a variety of
appropriate circuits for detecting the phase of the alternating current
power supply and providing appropriate biasing potentials to switching
means Q1 and Q2 such as at terminals E, F, G and H, respectively.
Switching control circuit 64 is advantageously divided into a first or
positive switching control subcircuit 65 and a second or negative
switching control subcircuit 66. Positive switching control subcircuit 65
provides voltage across terminals E and F which biases switching
transistors Q1 into a conductive mode during negative portions of the
alternating current. When switching means Q1 are in the conductive mode,
positively charged capacitor C1 discharges therethrough and the
discharging current is conducted through resistors R1, conductor 52 and
choke L1 to power lamp 32.
Positive switching control circuit 65 also effectively reverse biases
positive switching means Q1 during positive portions of the alternating
current from 34, thereby placing switching means Q1 into a nonconductive
mode when line voltage is positive and capacitor C1 is being positively
charged. The nonconductive mode of Q1 prevents excessive current from
flowing to lamp 32 which would otherwise occur by direct connection of
line to lamp 32.
Negative switching control 66 functions similar to positive switching
control 65 but in a complementary asynchronous manner. Switching control
66 provides voltage across terminals G and H which biases switching
transistors Q2 into a conductive mode during positive portions of the
alternating current. When switching means Q2 are in the conductive mode,
negatively charged capacitor C2 discharges through diodes D5 and D6,
resistors R2, switching transistors Q2, and choke L1 to power lamp 32.
Negative switching control 66 also effectively reverse biases negative
switching means Q2 during negative portions of the alternating current
supply by source 34, thereby placing switching means Q2 into a
nonconductive mode when line voltage is negative and capacitor C2 is being
negatively charged. The nonconductive mode of Q2 prevents excessive
current from flowing to lamp 32 which would otherwise occur by direct
connection of line to lamp 32.
FIG. 3 shows one specific form of circuit which can be used as positive
switching control 65. Such circuit includes an inductive coil L3 which
senses the phase of the incoming line voltage through transformer core 69.
Transformer core 69 is shared with coil L5 which is connected across the
incoming line voltage. The induced voltage in coil L3 swings positive and
negative depending on line voltage from current source 34.
The first side L3a of coil L3 is connected to the first plate of capacitor
C5, the anode of blocking diode D11, and to the emitter of transistor Q3.
The opposite or second side L3a of coil L3 is connected to a resistor R5
and the anode of blocking diode D9. Resistor R5 is also connected to the
anode of diode D11 and the base of transistor Q3. The cathode of diode D9
is connected to the second plate of capacitor C5 and to resistor R3. The
opposite side of resistor R3 is connected to terminal or conductor E which
is further connected to the bases of switching transistors Q1. The
collector of transistor Q3 is connected to F and conductor 52 of FIG. 2. A
resistor R4 is connected between the collector of Q3 and conductor E.
During positive portions of the a-c line voltage, the voltage induced
across coil L3 creates a positive voltage at terminal L3a and a negative
voltage at terminal L3b. The positive voltage at L3a is supplied to the
emitter of transistor Q3 and the first plate of capacitor C5. Positive
current flows through diode D11, resistor R5 and to negative terminal L3b
to reverse bias transistor Q3 into a nonconductive mode. Resistor R4
causes the potential across conductors E and F to be equal when transistor
Q3 is off, thus effectively biasing switching transistors Q1 into a
nonconductive mode so that positive capacitor C1 is charged and direct
line current is not applied to lamp 32.
When the alternating current goes into a negative portion of the a-c cycle
then L3b is relatively positive with respect to L3a. The greater voltage
thereat flows through resistor R5 to forwardly bias transistor Q3 into a
conductive mode. Positive current from the L3b side of coil L3 also flows
through diode D9, resistor R3 and forwardly biases switching transistors
Q1 into the conductive mode thereby discharging capacitor C1 therethrough
to lamp 32. Current supplied through resistor R3 is passed through diodes
D3 and D4 and back through transistor Q3 to the L3a side of coil L3.
FIG. 3 also shows one specific form of circuit which can be used as
negative switching control 66. Such circuit is conceptually similar to
switching control 65. Switching control 66 includes an inductive coil L4
also on core 69 and having a first side L4a and second side L4b.
The first side of coil L4 is connected to resistor R6 and the anode of
blocking diode D10. The second side L4b is connected to one side of
capacitor C6, the anode of blocking diode D12 and the emitter of
transistor Q4. The opposite side of capacitor C6 is connected to the
cathode of diode D10 and to one side of resistor R7. The opposite side of
resistor R7 is connected to conductor G and the bases of switching
transistors Q2. Resistor R6 is also connected to the cathode of blocking
diode D12 and to the base of transistor Q4. The collector of transistor Q4
is connected to conductor H and to conductor 60 of FIG. 2. A resistor R8
is connected between conductors G and H.
During positive portions of the a-c line voltage, the voltage induced
across coil L4 creates a positive voltage at L4a and a negative voltage at
L4b. The relatively positive voltage at L4a passes through resistor R6 and
forwardly biases transistor Q4 into a conductive mode. Positive current
also flows from side L4a through diode D10, resistor R7 to forwardly bias
switching transistors Q2, allowing discharge of capacitor C2 through lamp
32. Current through resistor R7 passes through diodes D7 and D8 and back
through transistor Q4 to side L4b of coil L4.
During negative portions of line a-c the first side L4a is negative
relative to side L4b. Negative current flows from L4a and increases
potential through resistor R6 and diode D12 to reverse bias transistor Q4
into a nonconductive mode. Resistor R8 causes terminals G and H to achieve
an approximately equal voltage which effectively biases switching means Q2
into a nonconductive mode thus preventing the negative line voltage from
being directly connected to lamp 32, and also allowing capacitor C2 to be
negatively charged.
From the above discussion it is apparent that switching control circuit 64
controls switching means Q1 and Q2 so that capacitors C1 and C2 are
alternately charged and discharged through Q1 and Q2 so that current flow
to lamp 32 is limited by the capacitance of capacitors C1 and C2. This
prevents excessive current flow through lamp 32 after startup when the
resistance across the lamp has been reduced by the greater concentration
of ions within lamp 32. At startup the resistance across lamp 32 is
relatively higher thus requiring a relatively higher voltage to achieve
ionization of the particular gas used in lamp 32. However, this voltage
increase is not needed when optimal efficiency is desired during normal
operation. Accordingly, it is desirable to include a suitable starting
circuit to temporarily boost the voltage applied to lamp 32.
FIG. 2 shows a starting circuit 31 useful as part of circuit 100 to power
120 volt metal halide lamps. Starting circuit 31 includes a triac or other
suitable bidirectional switching device T1. Triac T1 has its main terminal
one connected to the unrectified incoming line current coming from fusible
surge resistor FR1. The gate of triac T1 is connected to a connector D
which communicates a triac gating signal from the general control circuit
90 shown in FIG. 4 and hereinafter described. The main terminal two of
triac T1 is connected to a first side of a capacitor C3. The opposite
second side of capacitor C3 is connected to node 80 between the anode of
blocking diode D5 and the cathode of blocking diode D6. The cathode of
diode D5 is connected at node 81 to the anode of diode D2, a first side of
negative capacitor C2, and a first side of capacitor C4. The opposite
second side of capacitor C4 is connected to the anode of diode D6, and to
conductor 60 which is connected through resistors R2 to negative switching
means Q2.
Starting circuit 31 operates in ballast and starting circuit 100 in the
following manner. Soon after initiating current to circuit 100 the
generalized control circuit 90 of FIG. 4 provides a gating control signal
at conductor D which activates triac T1 and allows current to flow
therethrough. A positive portion of the line a-c flows through triac T1
and positively charges the first side of capacitor C3. The following
negative portion of the alternating current causes the first side of
capacitor C2 to be negatively charged and forces the previous voltage
differential across capacitor C3, thereby lowering the potential at node
80 below peak negative line voltage. Blocking diode D6 allows the negative
voltage at node 80 to be conducted to one side of capacitor C4. Capacitor
C4 holds the increased negative voltage until the next positive cycle. The
following positive portion of the alternating current causes negative
switching transistors Q2 to close thus discharging the increased negative
charge on capacitor C4 through to lamp 32. The simultaneous positive
charging of the first side of capacitor C3 further induces additional
negative charge from the second side of capacitor C2. Repeated cycling of
starting circuit 31 may be needed to achieve a voltage value sufficient to
start lamp 32, such as approximately three times line voltage or 510 volts
peak. The negative charge on capacitor C2 also discharges through diodes
D5 and D6 and transistors Q2 to lamp 32. Starting circuit 31 boosts the
negative voltage supplied through switching transistors Q2 until the
gating control signal from D is terminated.
The starting control and diagnostic circuit 90 shown in FIG. 4 will now be
described. Starting control and diagnostic circuit 90 is used to generate
an appropriate gating control signal at D in order to operate starting
circuit 31 during an appropriate startup period, such as, for instance, 30
seconds to several minutes. During this startup period, the particular
discharge lamp type being used achieves a sufficiently stable operation to
continue without the boosted voltage provided by starting circuit 31 or an
equivalent thereof. Starting control and diagnostic circuit 90 also
provides diagnostic information on run and startup indicators explained
below.
Starting control circuit 90 advantageously includes an induction coil L7
which shares core 69 with coil L5 thus providing circuit 90 with a supply
of power at appropriate voltage and current values. Coil L7 as used with
ballast 11 advantageously provides 6-8 volts and current of approximately
1/2 ampere. The first side of coil L7 is connected to node 91 and the
second side to node 92. Node 92 is connected to conductor or terminal C
which is connected to the output of surge resistor FR1.
The first side of coil L7 is connected to the anode of blocking diode D13
and to the cathode of blocking diode D14. Diodes D13 and D14 effectively
divide the output of coil L7 into positive and negative components,
respectively. Capacitor C7 is connected with a first side to the cathode
of diode D13 and the second side to conductor 93 which is directly
connected to node 92 and conductor C. Capacitor C8 is connected with a
first side to the anode of diode D14 and a second side connected to
conductor 93. Capacitors C7 and C8 smooth the respective positive and
negative half wave currents passed by diodes D13 and D14. The resulting
approximately positive and negative direct currents supplied by conductors
94 and 95 are used to power remaining components as described below.
Starting control and diagnostic circuit 90 includes a series of resistors
R9-R12 connected between the positive power supplied by conductor 94 and
the control ground potential existing on conductor 93. Each intermediate
node 96-98 is accordingly at a decreasing voltage. Zener diode D15 is
connected between node 96 and conductor 93 in order to accurately fix a
reference voltage for nodes 96-98.
Operational amplifier A1 is used to compare the voltage on conductor 99 to
the voltage at node 98. If the voltage on conductor 99 exceeds the voltage
at node 98 then there is a substantial positive current output from Al. If
the voltage on conductor 99 is less than the voltage at node 98 then there
is substantial negative current output from Al.
The signal on conductor 99 originates at conductor A which is the incoming
line voltage before surge resistor FR1. Conductor A is connected to
resistor R22 to provide surge protection. The output from resistor R22 is
connected to the anode of blocking diode D17. The cathode of diode D17 is
connected to conductor 99. Capacitor C9 is connected between conductor 99
and conductor 93 to smooth the positive portion of line voltage which
passes through diode D17. A relatively high resistance resistor R13 is
also connected between conductors 99 and 93 to allow capacitor C9 to
slowly discharge therethrough. During brief power interruptions, such as
less than 1 second in duration, capacitor C9 keeps the signal in conductor
99 sufficiently high to maintain continued operation. Blocking diode D16
assures that excessive positive voltages are not developed on conductor 99
by passing such through zener diode D15 to conductor 93.
The output from comparative operational amplifier A1 is connected to the
anode of blocking diode D20 and to one side of resistor R15. The other
side of resistor R15 is connected to the cathode of blocking diode D18.
The anode of diode D18 is connected to node 101. The cathode of blocking
diode D20 is connected in series with resistor R14 and light emitting
diode LED 1 to connector 93. A positive output from A1 thus passes through
D20, R14 and lights LED 1 to indicate that power is being used by lamp 32
as will be explained more fully below.
Starting control and diagnostic circuit 90 also includes a second
comparative operational amplifier A2. One input to A2 is connected to an
appropriate reference voltage developed at node 97. The other input to A2
is connected to node 101 which is typically provided with a positive
voltage from conductor 94 through a high resistance value resistor R16.
Node 101 is also connected to one side of a capacitor C10. The other side
of capacitor C10 is connected to conductor 93.
Amplifier A2 controllably provides an output signal along conductor 102
which is connected to the anode of blocking diode D19 allowing positive
output to pass therethrough to node 103. Node 103 is connected in series
to resistor R19, light emitting diode LED 2, and conductor 93. Node 103 is
also connected to one side of resistor R18, the other side of which is
connected to the base of a switching device such as transistor Q5. A
resistor R20 is connected between the base of Q5 and conductor 93.
The collector of transistor Q5 is connected to conductor 94 through
resistor R17. The emitter of transistor Q5 is connected to conductor D
which carries the starting circuit control signal to starting circuit 31.
The emitter of transistor Q5 is also connected to conductor 93 through
resistor R21.
The operation of starting control and diagnostic circuit 90 will now be
fully described. During the initial phases of startup, the amount of
current flowing through resistor FR1 are small because lamp 32 has not
fired, thus keeping the voltage drop thereacross small. The voltage
supplied at C is thus very close to the voltage at A resulting in inputs
to amplifier A1 which are approximately equal, or with node 98 somewhat
lower. This produces no output from A1 and LED 1 is not initially
illuminated, thus indicating that lamp 32 has not started.
Also upon initial startup, positive current flows through conductor 94, and
resistor R16 to begin charging capacitor C10. The amount of charge
developed on C10 does not increase at a substantial rate until the output
from amplifier A1 becomes positive as a result of lamp ignition.
With firing of lamp 32 and the increased current flow therethrough, a
substantial voltage drop occurs across surge resistor FR1 thus increasing
the relative voltage at A as compared to C. The increased voltage at A
increases the voltage in conductor 99 and causes the output of A1 to go
positive thus lighting LED 1 which acts as an indicator light that lamp 32
is functioning. The positive output from A1 creates a potential at the
cathode of blocking diode D18 which prevents leakage therethrough, and
directs substantially all current passing through resistor R16 to charge
capacitor C10.
Amplifier A2 receives a relatively fixed voltage input from node 97.
Initially, the secondary input from node 101 is at a relatively lower
potential since capacitor C10 is not yet charged due to the delay required
to fire the lamp and the small current passed through resistor R16. Thus,
during this initial startup period A2 produces a positive output signal to
conductor 102. The positive, output signal passes through diode D19,
resistor R19 and lights LED 2 which acts as a indicator light for the
startup period. The output from A2 also biases transistor Q5 into a
conductive mode and a startup control signal is sent to triac T1 via
conductor D, thus creating the desired startup voltage for lamp 32 as
explained above.
After an appropriate period of time, capacitor C10 becomes sufficiently
charged so that the voltage at node 101 exceeds the voltage at node 97.
This causes the output from amplifier A2 to go negative thus terminating
the operation of LED 2 and zero biasing transistor Q5 thus stopping the
startup control signal to triac T1. The voltage drop across surge resistor
FR1 continues with substantial current flow through lamp 32 continuing the
illumination of LED 1 to indicate lamp operation even though the startup
period indicator LED 2 is no longer illuminated. The operational sequence
described above for circuit 90 is repeated each time startup of lamp 32 is
required.
The preferred circuit 100 according to this invention as described herein
and illustrated in FIGS. 2-4 is advantageously constructed for use as a
ballast with nominal 120 volt, 400 watt metal halide discharge lamps
currently availbel in the U.S. The values of components listed below in
TABLE I are believed most advantageous for such application, although
there will be many alternative values and circuit modifications and
equivalents which will be obvious to those skilled in the art.
TABLE I
______________________________________
RESISTORS
FR1 0.2 ohm
R1, R2 0.22
R3 100 ohm
R4 100 ohm
R5 200 ohm
R6 220 ohm
R7 8.2 ohm
R8 100 ohm
R9 1K ohm
R10-R12 10K ohm
R13 10M ohm
R14 10M ohm
R15 820 ohm
R15 1K ohm
R16 30M ohm
R17 68 ohm
R18 1K ohm
R19 820 ohm
R20 10K ohm
R21 330 ohm
R22 10K ohm
CAPACITORS
C1 330 microfarads
C2 330 microfarads
C3 30 microfarads
C4 10 microfarads
C5, C6 1000 microfarads
C7 470 microfarads
C8 100 microfarads
C9 0.1 microfarads
C10 0.47 microfarads
INDUCTORS
L1 5 millihenries
______________________________________
FIG. 5 shows an alternative circuit 200 which can be used in lieu of the
circuit shown in FIG. 2 in conjunction with the circuitry shown in FIGS. 3
and 4 to produce a switched capacitive ballast which can be used with
nominal 240 volt a-c power for 400 watt metal halide discharge lamps. The
conductors or terminals lettered A, C, D, E, F, G, H, and I connect with
the circuits of FIGS. 3 and 4 at the similarly designated points in a
manner similar to the circuit shown in FIG. 2 and described above.
A source of alternating current 201 is connected across terminals 202 and
203. Typically the neutral or common side of current source 201 is
connected to terminal 203 and the hot or voltage varying side is connected
to terminal 202. A fusible surge resistor FR2 is placed in series between
incoming line voltage and conductor C.
Circuit 200 includes a first or positive rectifying means such as blocking
diode D30 which is connected with the anode to surge resistor FR2.
Blocking diode D30 passes only the positive portions of the incoming
alternating current therethrough. Circuit 200 is also provided with a
second or negative rectifier such as blocking diode D31. Diode D31 is
oppositely oriented with its cathode connected to incoming current from
source 201 so that only negative portions thereof are passed therethrough.
Circuit 200 includes positive charge storage means such as capacitors C21
and C22. Capacitor C21 has a first side connected to the output or cathode
of diode D30 to receive positive current therefrom. The cathode of diode
D30 and the first side of capacitor C21 are also connected to the anode of
blocking diode D32. The cathode of diode D32 is connected to conductor
210. The second side of capacitor C21 is connected to the anode of
blocking diode D33 and to the cathode of blocking diode D35. The anode of
diode D35 is connected to conductor 211 which connects to terminal 203.
The cathode of diode D33 is connected to a first side of capacitor C22 and
to the anode of blocking diode D34. The cathode of diode 34 is connected
to conductor 210. The second side of capacitor C22 is connected to
conductor 211. Conductor 211 is also connected to a second side or
electrode of discharge lamp 232 at second terminal 233.
This arrangement of diodes D32-D35 and capacitors C21 and C22 allows
capacitors C21 and C22 to be charged in series and discharged in parallel.
During charging, incoming positive portions of the supply current from
source 201 pass through diode D30 to the first side of capacitor C21.
Positive charge is also conveyed through diode D33 to charge the first
side of capacitor C22 in series with C21. The voltages across capacitors
C21 and C22 are shared according to well known electrical principals.
During discharge of capacitors C21 and C22, the preferably equally shared
voltage is concurrently directed onto line 210 in parallel. Capacitor C21
discharges through diode D32 and capacitor C22 discharges through diode
D34. Diode D33 isolates the first side of C22 from the second side of C21
during discharge. This arrangement for the positive charge storage means
is advantageous where lamp 232 does not require operating voltages which
would otherwise be achieved by direct connection of a single capacitor
between line 210 and line 211, similar to the circuit of FIG. 2.
Circuit 200 also includes a negative charge storage means such as
capacitors C23 and C24. The first side of capacitor C23 is connected to
the output or anode of rectifying diode D31. The opposite or second side
of capacitor C23 is connected to the anode of blocking diode D39 and to
the cathode of blocking diode D37. The cathode of diode D39 is connected
to conductor 211. The anode of diode D31 is connected to the cathode of
diode D36. The anode of diode D36 is connected to conductor 212 and to the
anode of blocking diode D38. The cathode of diode D38 is connected to the
anode of diode D37 and to the first side of capacitor C24. The second side
of capacitor C24 is connected to conductor 211. This arrangement of
capacitors C23 and C24 and diodes D36-D39 also allows capacitors C23 and
C24 to be charged in series and discharged in parallel. Description of the
similar operation of capacitors C21 and C22 is given above and will not be
repeated for C23 and C24.
Positive conductor 210 is connected to a positive switching means such as
switching transistors Q10 which are in parallel with collectors of each
connected to conductor 210. The bases of switching transistors Q10 are
also connected in parallel to conductor E which is connected to positive
switching control circuit 65 of FIG. 3 which provides a switching control
signal as described above.
The emitters of switching means Q10 are connected through parallel
resistors R30 to conductor F. Conductor F is connected to positive
switching control circuit 65 as described above with respect to FIG. 3.
Conductor F is also connected to an inductive coil or choke 240 which
smooths the power supplied therethrough to first terminal or electrode 234
of discharge lamp 232. Blocking diodes D42 and D43 are connected in series
between the parallel bases of switching transistors Q10 and conductor F to
allow biasing control current to flow therethrough.
Negative conductor 212 is similarly connected to a negative switching means
such as switching transistors Q11. The emitters of switching transistors
Q11 are connected in parallel through parallel resistors R31 to line 212.
The bases of switching transistors Q11 are connected in parallel to
conductor G which is connected to the negative switching control circuit
66 as shown in FIG. 3 and described above. Conductor 212 is directly
connected to conductor H which is also connected to the negative switching
control circuit 66 of FIG. 3. The collectors of switching transistors Q11
are connected in parallel via conductor F to choke 240 and lamp 232.
FIG. 5 further shows a starting circuit 250 which is used to increase the
starting voltage applied across discharge lamp 232 during negative
portions of the alternating current supplied by current source 201.
Starting circuit 250 includes a triac T2 or similar electronic switching
means. The main one terminal of triac T2 is connected to conductor C. The
main two terminal of triac T2 is connected to a first side of capacitor
C26. The gate terminal of triac T2 is connected to conductor D which
provides a gating control signal such as described above and illustrated
at FIG. 4.
The second side of capacitor C26 is connected to the cathode of blocking
diode D40 and to the anode of blocking diode D41. The cathode of diode D41
is connected to conductor 211. The anode of diode D40 is connected to
conductor 212. A capacitor C25 is connected in parallel with blocking
diode D36 described above.
The operation of starting circuit 250 will be described in conjunction with
the operation of remaining components of ballast circuit 200. Operation of
circuit 200 is initiated by starting alternating current source 201 or by
closing an appropriate switch (not shown). Initial starting of starting
and control circuit 90 of FIG. 4 causes a gating control signal to be
carried by conductor D to triac T2 thus placing the triac in a conductive
mode. A negative portion of the alternating input current cause capacitors
C23 and C24 to be charged in series. As the line current swings positive
capacitor C26 is charged with its first side positive and second side at
common or ground potential because of connection to conductor 211 through
blocking diode D41. As the input current swings negative again the voltage
differential across capacitor C26 is increased because the first side of
the capacitor must respond to the applied line voltage and the previous
charge is not quickly dissipated. This effectively adds the voltage swing
to the previous capacitor voltage differential. In the nominal 240 volt
circuit described in FIG. 5 the voltage across C26 is changed from -340
volts to approximately -680 volts. This increased negative potential at
the second side of capacitor C26 causes negative current to flow through
blocking diode D40 to charge the second side of capacitor C25 to
approximately -680 volts with respect to ground, in series with capacitors
C23 and C24. The following positive cycle changes the potential on the
first side of capacitor C23 from -340 volts to -170 volts with respect to
ground. Capacitors C23 and C25 then discharge in series through
transistors Q11 to lamp 232 providing approximately -510 volts. Several
cycles of a-c current may be needed to bring the second side of capacitor
C25 up to the -510 volts output desired. The specific voltage needed is
dictated by the lamp being used. For a 400 watt metal halide lamp of
common use in the United States, it is necessary to apply approximately
500 volts in order to arc the lamp for startup. Repeated arcing is
necessary in most cases. Accordingly, capacitor C25 is charged to about or
somewhat more negative potential than -500 volts at its second side and
then is discharged during positive portions when switching transistors Q11
are conductive. This boosted startup voltage on the negative side of
circuit 200 allows lamp 232 to be started.
Upon startup the gas or gases contained in a discharge lamp become ionized
and the resistance across the lamp decreases and increased current begins
to flow therethrough. The general control circuit 90 senses the increased
current flow via the substantial voltage drop across surge resistor FR2.
This causes the output from operational amplifier A1 to go high and light
LED 1, which indicates that the discharge lamp is drawing current. The
outputs from amplifier A1 causes the startup period defined by resistor
R16 and capacitor C10 to begin. When capacitor C10 is sufficently charged
the output of amplifier A2 goes low and the gating control signal from the
emitter of transistor Q5 onto conductor D also goes low thus placing triac
T2 into a nonconductive mode, thus ending the startup period.
During and after the startup period, the positive capacitors C21 and C22
are charged in series during positive portions of the incoming alternating
current. Capacitors C21 and C22 are discharged in parallel during negative
portions of the alternating current. Capacitors C21 and C22 are charged in
series and discharged in parallel because the voltage needed to properly
operate discharge lamp 232 only requires less than .+-.170 volts after
ionization has occurred. Thus the peak line voltage of 340 volts is not
needed and is reduced using the series-parallel charging and discharging
of capacitors C21 and C22.
Similarly, capacitors C23 and C24 are charged negatively in series during
negative portions of the alternating current. Capacitors C23 and C24 are
discharged in parallel during positive portions of the alternating current
when switching transistors Q11 are biased into a conductive mode.
The alternating asynchronous operation of the positive and negative sides
of circuit 200 allows current flow through lamp 232 to be limited to the
charge which can be effectively discharged from positive capacitors C21
and C22 during negative portions, and negative capacitors C23 and C24
during positive portions of the power from alternating current supply 201.
The switching control circuits 64 described herein and shown in FIG. 3 are
also used to control switching transistors Q10 and Q11 in a manner the
same as described for switching transistors Q1 and Q2, above, and will not
be repeated here for circuit 200 since the operation is the same.
Similarly the general control circuit 90 is also connected to circuit 200
as indicated in the FIGS. in an analogous way to its use with the circuit
of FIG. 2. Operation is equivalent to the description given with respect
thereto.
Table II shown below gives preferred values of capacitance, inductance and
resistance which may be used for the components shown in circuit 200 of
FIG. 5.
TABLE II
______________________________________
RESISTORS
FR2 0.4 ohm
R30 and R31 0.22 ohm
CAPACITORS
C21-C24 165 microfarads
C25 10 microfarads
C26 30 microfarads
INDUCTORS
L8 5 millihenries
______________________________________
FIG. 6 shows a further embodiment capacitive ballast circuit 300 according
to this invention. Circuit 300 includes a source of alternating current
301 connected across terminals 302 and 303. A power on-off switch 304 can
advantageously be provided to allow controlled supply of current to
remaining portions of circuit 300. Circuit 300 is designed for use with a
120 volt rms single phase power supply with terminal 303 being common and
terminal 302 experiencing the alternating voltage. Terminal 303 is
connected to a conductor 305 which is connected to a number of components
described below including one side 306b of an electrical discharge lamp
306. The opposite side 306a of lamp 306 is connected to remaining portions
of circuit 300 which are used to startup and control current flow through
lamp 306.
The output side of switch 304 is connected to conductor 310 which and is
connected to first sides of induction coils L11 and L12 which preferably
form part of a transformer 312 having a core 313, or equivalents thereto.
The second side of coil L11 is connected to common via conductor 305.
Coil L12 is part of a starting circuit 314. Coil L12 has a greater number
of coils thereon than L11 to provide an increased voltage thereacross such
as in the range of approximately .+-.500 volts peak, from the .+-.170
volts peak alternating current supplied by source 301. The second side of
coil L12 is advantageously connected to a manual starting switch 315 which
can be manually closed to provide increased starting voltage to both
positive and negative sides of ballast circuit 300 as further explained
below.
Switch 315 is connected to the anode of blocking diode D60 and to the
cathode of blocking diode D61. The cathode of diode D60 is connected in
parallel to a first side of a capacitor C50 and to a first side of
resistor R50. The anode of diode D61 is connected in parallel to a first
side of capacitor C51 and to a first side of resistor R51. The second side
of resistor R50 is connected to conductor 320 and the second side of
resistor R51 is connected to conductor 321. The second sides of capacitors
C50 and C51 are connected to conductor 305.
Circuit 300 further includes a means for dividing incoming line current
into positive and negative components corresponding to positive and
negative currents flowing during positive and negative portions of the
alternating current, respectively. Such means for dividing the alternating
current includes blocking diodes D62 and D63. The anode of diode D62 and
cathode of diode D63 are connected to conductor 310 through a surge
resistor R52. The cathode of diode D62 is connected to a first side of
positive capacitor C52. The second or opposite side of capacitor C52 is
connected to common using conductor 305. Diode D62 allows positive current
to flow therethrough to positively charge capacitor C52. The anode of
diode D63 is connected to the first side of negative capacitor C53. The
second or opposite side of capacitor C53 is connected to common using
conductor 305. Diode D63 allows negative current to flow from conductor
510 therethrough to negatively charge capacitor C53.
The cathode of blocking diode D62 and the first side of capacitor C52 are
connected to the anode of a further blocking diode D64. The cathode of
diode D64 is connected to conductor 320. Diode D64 prevents flow of charge
from starting capacitor C50 to positive capacitor C52.
The anode of blocking diode D63 and the first side of capacitor C53 are
connected to the cathode of blocking diode D65. The anode of diode D65 is
connected to conductor 321. Diode D65 prevents flow of charge from
starting capacitor C51 to negative capacitor C53.
The output from the cathode of diode D64 is connected by conductor 320 to
an appropriate positive switching device, such as switching transistors
Q31 which are connected in parallel. Conductor 320 is connected to the
collectors of transistors Q31. The emitters of switching transistors Q31
are connected to the first sides of parallel resistors R53. The opposite
sides of resistors R53 are connected to conductor 340. A blocking diode
D66 is connected in parallel across the collector and emitter of switching
transistor Q31a with the cathode of diode D66 connected to the collector.
A resistor R54 is connected in parallel between the bases of transistors
Q31 and the emitter of transistor Q31b. Blocking diodes D68 and D69 are
connected in series between the base of transistors Q31 and conductor 340
with the cathodes oriented toward conductor 340. The bases of positive
switching transistors Q31 are connected in parallel to a positive
switching control subcircuit 350, which will be described more fully
below. The emitters of switching transistors Q31 are also connected to
subcircuit 350 through resistors R53 and conductor 340.
The output from the anode of blocking diode D65 is connected by conductor
321 to an appropriate negative switching device, such as switching
transistors Q12. Transistors Q12 are connected in parallel to conductor
321 via parallel resistors R55 connected to the emitters of transistors
Q12. The collectors of transistors Q12 are connected to conductor 340. A
blocking diode D67 is connected in parallel across the emitter and
collector of switching transistor Q12a with the anode connected to the
emitter and the cathode connected to the collector. A resistor R56 is
connected between the emitter and base of transistor Q12b. Blocking diodes
D70 and D71 are connected in series from the base of transistors Q12 to
conductor 321 with the cathodes oriented toward conductor 321. The bases
of switching transistors Q12 are connected to a negative switching control
subcircuit 360 which will be described more fully below. The emitter of
switching transistors Q12 are also connected to subcircuit 360 through
resistors R55.
The current outputs from switching means Q31 and Q12 are conducted by
conductor 340 through an inductive choke L13 to discharge lamp 306.
Switching control circuits 350 and 360 are conceptually and structurally
similar. Each is designed to properly sense the phase of the incoming
current supplied by source 301. During positive portions of the a-c
current the positive switching control circuit 350 reverse biases positive
switching means Q31 into a nonconductive mode. During negative portions of
the incoming current circuit 350 forwardly biases switching means Q31 into
a conductive mode. Negative switching control circuit 360 operates
asynchronously to circuit 350 controlling negative switching means Q12
into a conductive mode during positive portions and into a nonconductive
mode during negative portions. Having briefly outlined the overall
function of control circuits 350 and 360, the structures thereof will now
be described in detail.
Positive switching control circuit 350 includes an inductive coil L14 which
can advantageously be on the secondary side of transformer core 313. Coil
L14 develops appropriate control circuit potential and alternating current
such as, for example, 6 volts and 1/2 amp, respectively. The first side of
coil L14 is connected to the emitter of an appropriate switching device
such as transistor Q13. The collector of transistor Q13 is connected to
conductor 340. Transistor Q13 is the primary element in circuit 350
serving to switch coil L14 to positive switching transistors Q31 and
provide a forward bias thereon during negative portions of the alternating
current.
The second side of coil L14 is connected to the anode of blocking diode D72
and to a first end of resistor R57. The cathode of diode D72 is connected
to one side of capacitor C54 and to resistor R59. Resistor R59 is also
connected to the bases of positive switching transistors Q31, and to the
anode of blocking diode D68. The cathode of diode D68 is connected to the
anode of blocking diode D69. The cathode of diode D69 is connected to
conductor 340.
Circuit 350 is further constructed by connecting the second end of resistor
R57 to the cathode of blocking diode D73, the base of transistor Q13, and
one end of resistor R58. The anode of diode D73 is connected to the
emitter of transistor Q13 and to the opposite end of resistor R58. The
second side of capacitor C54 is also connected to the emitter of
transistor Q13.
Negative switching control circuit 360 includes an inductive coil L15 which
is also advantageously on the secondary side of transformer core 313. Coil
L15 develops potential and current similar to L14. The first side of coil
L15 is connected to the anode of blocking diode D74 and the second side of
coil L15 is connected to the emitter of transistor Q14. The collector of
transistor Q14 is connected to the emitters of negative switching
transistors Q12 via conductor 321 and resistors R55. The cathode of diode
D74 is connected to a first side of capacitor C55 and to a first end of
resistor R62. The opposite end of resistor R62 is connected to the bases
of negative switching transistors Q12 and to the two series blocking
diodes D70 and D71 oriented with the anodes toward resistor R62. The
cathode of blocking diode D70 is connected to conductor 321. The second
side of capacitor C55 is connected to the anode of blocking diode D75, the
emitter of transistor A14, and the second side of coil L15. The cathode of
diode D75 is connected to the base of control transistor Q14. The base of
transistor Q14 is also connected to resistors R61 and R60. The opposite
end of resister R61 is connected to the emitter of Q14 and the opposite
end of resistor R60 is connected to the first side of coil L15.
Circuit 350 operates in the following manner. Coil L14 generates an
appropriate alternating voltage thereacross in response to the induced
magnetic flux in core 313. Transistor Q13 is reverse biased during
positive portions of the line a-c in the following manner. During positive
portions the first side of coil L14 (connected to the emitter of Q13) is
positive relative to the second side of coil L14. The lower potential of
the second side is connected through resistors R57 and diode D73 to the
high side of coil L14. The base of transistor Q13 is at the potential
established between resistor R57 and diode D73, which must be at a
potential less than the emitter voltage because of the voltage drop across
each. Transistor Q13 is thus biased into the nonconductive mode. Meanwhile
diode D72 prevents current from flowing therethrough because of the
relatively low potential at the anode thereof. The bias voltage of
transistors Q31 is equalized by the connection thereacross by resistor
R54, thus effectively zero biasing them into a nonconductive mode.
During negative portions of the line a-c the second side of coil L14 is
relatively high compared to the first side of L14. This causes positive
current to flow through resistors R57 and R58 to the low side of coil L14.
The potential at the emitter of transistor Q13 is low because of the
direct connection to the first side of 214. The base voltage is higher
because of the connection between the base and the node existing between
resistors R57 and R58. Transistor Q13 is thus forwardly biased into a
conductive mode. Current can accordingly flow from the high side of coil
L14 through diode D72, resistor R59, diodes D68 and D69 and back through
transistor Q13. This flow of current is smoothed by capacitor C54. The
resulting potential at the bases of positive switching transistors Q31 is
higher than at the emitters because of current flow through resistor R54,
thus forwardly biasing transistors Q31 into a conductive mode.
Negative switching control circuit 360 operates substantially the same as
circuit 350 except that the first side of coil L15 is connected to the
blocking diode D74 and the second side of L15 to the emitter of transistor
Q14. This is reverse of the arrangement in circuit 350 thereby causing
negative switching control circuit 360 to forward bias switching
transistors Q12 into a conductive mode during positive portions of the
line a-c, and to zero bias transistors Q12 into a nonconductive mode
during negative portions.
The operation of remaining portions of ballast and starting circuit 300
will now be considered in greater detail. During positive portions of line
current switching transistors Q31 are biased into a nonconductive mode,
and switching transistors Q12 are biased into a conductive mode as just
described. During negative portions transistors Q31 are biased conductive
and transistors Q12 are biased nonconductive. This asynchronous operation
allows capacitor C52 to positively charge and capacitor C53 to discharge
its negative charge through transistors Q12 during positive portions.
Conversely during negative portions of line a-c capacitor C53 charges
negatively and capacitor C52 discharges its positive charge through
transistors Q31.
Positive capacitor C52 discharges during negative portions of line a-c
during which terminal 303 is at a higher voltage than terminal 302.
Nonetheless, positive charge exists on the first side of capacitor C52
because of blocking diode D62. Such is discharged through diode D64,
switching transistors Q31, resistors R53, coil L13, discharge lamp 306
back to common terminal 303. Negative capacitor C53 discharges during
positive portions during which terminal 302 is at a relatively higher
voltage than common terminal 303. Nonetheless, the negative charge exists
on the first side of capacitor C53 because of blocking diode D63. Such is
discharged through diode D65, resistors R55, transistors Q12, coil L13,
discharge lamp 306 back to common terminal 303.
Starting circuit 314 supplements the voltage supplied through transistors
Q31 and Q12 to lamp 306. This is accomplished by charging capacitor C50
during positive portions to a relatively high starting voltage and then
first discharging capacitor C50 through transistors Q31 during negative
portions when transistors Q31 are in the conductive mode. Conversely,
circuit 314 also supplements the negative charge and starting voltage by
charging capacitor C51 during negative cycle portions to a relatively high
starting voltage and then discharging capacitor C51 through transistors
Q12 during positive portions when transistors Q12 are in a conductive
mode. Starting circuit 314 is manually controlled by switch 315.
Table III presents preferred values of resistance, inductance and
capacitance for resistors, inductors and capacitors useful in a preferred
form of circuit 300.
TABLE III
______________________________________
RESISTORS
R50, R51 100 ohm
R52 0.5 ohm
R53, R55 0.15 ohm
R54, R56 100 ohm
R57, R60 47 ohm
R58, R61 22 kilohm
R59, R62 47 ohm
CAPACITORS
C50, C51 10 microfarads
C52, C53 330 microfarads
C54, C55 1000 microfarads
INDUCTORS
L13 5 millihenries
______________________________________
A portion of a still further embodiment ballast and starting circuit 400
according to this invention is shown in FIG. 7. Current is supplied by
current source 401 to terminals 402 and 403. On-off switch 404 is also
advantageously provided to control current flow from source 401. Fusible
surge resistor FR3 is connected at one end to terminal 402. The opposite
end of surge resistor FR3 is connected to the anode of blocking diode D90
and to the cathode of blocking diode D91. Diodes D90 and D91 divide the
alternating line current into positive and negative portions,
respectively.
The cathode of diode D90 is connected to first sides of capacitors C60 and
C61, and to the anode of blocking diode D94. The cathode of diode D90 is
also connected by optional conductor A-1 to the cathode of blocking diode
D92, to the anode of blocking diode D95, and to the first side of
capacitor C62. Optional conductor or jumper A-1 and other jumpers are used
as described below to convert circuit 400 for different voltages and
wattages of metal halide discharge lamps 409. Optional conductors or
jumpers labelled A, B, and Z will be hereinafter described for use with
appropriate lamp types as also hereinafter described.
The second side of capacitor C61 is connected to the anode of blocking
diode D92 and to the cathode of blocking diode D93. The second side of
capacitor C60 is optionally connected by jumper B-1 to the second side of
capacitor C61 when lamp 409 is of a type requiring B jumper connections.
The second side of capacitor C61 is also optionally connected by jumper
A-2 to the second side of capacitor C62 when lamp 409 is of a type
requiring A jumpers. The second side of capacitor C62 and the anode of
blocking diode D93 are both connected to conductor 412. A further
capacitor C63 has a second side which is also connected to conductor 412.
The first side of capacitor C63 is optionally connected by jumper B-2 to
the first side of capacitor C62 and the anode of blocking diode D95. The
cathodes of diodes D94 and D95 are both connected to conductor 420.
Capacitors C60-C63 serve to store positive charge passing through diode
D90. Diodes D92-D95 route current for charging and discharging capacitors
C60-C63, as will be more fully explained below in connection with
operation of circuit 400. Conductor 420 conducts positive change from
capacitors C60-C63 to an appropriate positive switching means such as
positive switching transistor Q21.
The negative current flowing through diode D91 is supplied to an
arrangement of blocking diodes D96-D99 and capacitors C64-C67,
conceptually similar to the arrangement just described for the positive
current output flowing from diode D90. The anode of diode D91 is connected
to the first sides of capacitors C64 and C65, and to the cathode of
blocking diode D96. The anode of diode D96 is connected to conductor 430.
The second side of capacitor C65 is connected to the anode of blocking
diode D99 and to the cathode of blocking diode D98. The second side of
capacitor C64 is optionally connected by jumper B-3 to the second side of
capacitor C65 to place it in parallel therewith when lamp 409 is of a type
requiring B jumpers to be connected. The cathode of diode D99 is connected
to conductor 412. The anode of diode D98 is connected to the cathode of
diode D97 and to the first side of capacitor C66. The second side of
capacitor C66 is connected to conductor 412. Capacitor C67 is connected
with a second side to conductor 412. The anode of blocking diode D96 and
the anode of diode D97 are connected to conductor 430.
Optional jumper A-3 is connected between the second side of capacitor C65
and conductor 412 when lamp 409 is of a type requiring A jumpers. Optional
jumper A-4 is connected from the anode of diode D91 to the first side of
capacitor C66 when lamp 409 requires A jumpers. Optional jumper B-3 is
connected from the second side of capacitor C64 to the second side of
capacitor C65 placing such capacitors in parallel when lamp 409 requires B
jumpers to be connected. Optional jumper B-4 is connected between the
first sides of capacitors C66 and C67 to place them in parallel also when
B jumpers are required.
The assembly of capacitors C64-C67 and diodes D96-D99 allows negative
current flowing through diode D91 to be stored in such capacitors, and be
discharged therefrom through a negative switching means such as negative
switching transistor Q22.
Positive switching transistor Q21 is connected in circuit 400 with its
collector connected to conductor 420 and the emitter connected to a first
end of resistor R70. The second end of resistor R70 is connected to
conductor 425 which supplies current through induction coil or choke L16
to discharge lamp 409. The base of transistor Q21 is connected to the high
or positive side of a positive switching control circuit such as 65 shown
in FIG. 3 at conductor E. The positive switching control circuit 65 is
also connected to conductor 425 by conductor F. The voltage differential
developed by circuit 65 across E and F is used to appropriately bias
transistor Q21 into a conductive mode during negative portions of incoming
a-c, and into a nonconductive mode during positive portions of incoming
a-c.
A blocking diode D100 is connected in parallel with switching transistor
Q21 with the cathode connected to conductor 420 and the anode connected to
conductor 425. Two blocking diodes in series D101 and D102 are connected
between the base of Q21 and conductor F.
Negative switching transistor Q22 is connected in circuit 400 in a manner
equivalent to that described in connection with positive switching
transistor Q21 with modification for the negative instead of positive
current being switched thereby. Negative current is supplied to the
emitter of transistor Q22 from conductor 430 through resistor R71. The
collector of transistor Q22 is connected to conductor 425 in order to
supply current to lamp 409. The base of transistor Q22 is connected to a
suitable negative switching control circuit such as at G of circuit 66
shown in FIG. 3. Negative switching control circuit 66 is also connected
at H to conductor 430. The voltage across G and H provide an appropriate
biasing voltage to place transistor Q22 into a conductive mode during
positive portions of the a-c from source 401, and into a nonconductive
mode during negative portions of a-c.
A blocking diode D103 is connected in parallel with switching transistor
Q22 with anode to conductor 430 and cathode to conductor 425. Two blocking
diodes 104 and 105 are connected in series with anodes to the base of Q22
and cathodes toward conductor 430.
Ballast and starting circuit 400 further includes a starting circuit 450
used to boost the voltage applied across the electrodes of lamp 409 during
startup. Starting circuit 450 is connected to apply boosted voltage only
to the negative side of circuit 400. Equivalent circuitry (not shown) can
alternatively be provided to the positive side either with or without
circuit 450.
Starting circuit 450 includes a silicon controlled rectifier SCR-1
connected with the anode thereof to conductor 430. The cathode of SCR-1 is
connected to the anode of blocking diode D107, the first side of capacitor
C69, and to terminal C of FIG. 4. The gate and cathode of SCR-1 is
connected across one side of pulse transformer 701. The opposite side of
pulse transformer 701 is connected across terminals C and D of FIG. 4. The
second side of capacitor C69 is connected to conductor 412. The cathode of
diode D107 is connected to the anode of blocking diode D106 and to the
second side of capacitor C68. The first side of capacitor C68 is connected
to the output side of surge resistor FR3. The cathode of diode D106 is
optionally connected by either jumper Z or jumper A-5 to conductor 412 or
the first side of capacitor C65, respectively.
Ballast and starting circuit 400 is designed for use with two different
discharge lamp wattage models, 400 watts and 1000 watts. The 400 watt lamp
can be operated by circuit 400 using alternating current sources having
rms voltages of 120, 240 and 277 volts. The 1000 watt lamp can be operated
by circuit 400 using alternating current sources having rms voltages of
240, 277 and 480 volts. In each case special or optional connections must
be made to properly adapt circuit 400 for operation of the chosen lamp at
the chosen voltage. FIG. 7 shows a chart indicating the type of jumpers
which must be provided in order to adapt circuit 400 for the particular
lamp and current source being used.
When a 400 watt lamp is used with 120 volt rms current then it is necessary
to connect jumper types A and B. Type A jumpers include jumpers A-1
through A-5 which must all be connected in order to meet the type A jumper
requirement. Type B jumpers include jumpers B-1 through B-4 which must all
be connected in order to meet the B requirement. When a 400 watt lamp is
used with a 240 volt rms current supply, it is necessary to connect type B
jumpers and the single type Z jumper. Type A jumpers are not connected in
such application. When the 400 watt lamp is used with a 277 volt rms
current source then circuit 400 is adapted by only connecting the Z
jumper.
Use of 1000 watt metal halide discharge lamps with circuit 400 requires a
different selection of jumpers than when using the 400 watt lamp. The 1000
watt lamp and 240 volt rms current source requires connecting both jumpers
types A and B. The 1000 watt lamp with a 277 volt rms current source
requires using only the type A jumpers. The 1000 watt lamp with a 480 volt
rms current source requires connection of both types B and Z jumpers only.
The operation of circuit 400 will now be explained. As with previously
described embodiments of this invention, circuit 400 first divides the
incoming alternating current from source 401 into a positive component and
a negative component using blocking diodes D90 and D91, or some other
suitable means for dividing the alternating current. The positive current
supplied during positive portions of the alternating current passes
through diode D90 and is charged in the appropriate capacitors C60-C63
depending upon the optional jumper connections required for the lamp and
current source being employed. When jumpers type A are only being used,
such as with a 1000 watt lamp at 277 volts rms, then positive current flow
through diode D90 causes charging of capacitors C61 and C62 in parallel.
Capacitors C61 and C62 also discharge in parallel. When jumper types A and
B are both connected then capacitors C60-C63 all charge and discharge in
parallel. When jumper types B and Z are both used then capacitors C60 and
C61 charge as a parallel unit in series with capacitors C62-C63 as a
parallel unit. Capacitors C60-C63 all discharge in parallel. When only
type Z jumpers are used then only capacitors C61 and C62 are effectively
charged in series, and discharged in parallel.
The charging and discharging of negative capacitors C64-C67 is equivalent
to the charging and discharging just described for the various jumper
combinations for positive capacitors C60-C63. In all cases capacitance is
produced which is needed to effectively power the associated lamp and the
operating potential is maintained at an appropriate level without applying
unnecessarily high voltage across the lamp, thus optimizing the operating
efficiency of the ballast circuit.
In any of the capacitance options indicated above, the positive capacitors
charge positively during positive portions of the alternating current, and
discharge during negative portions. Conversely, the negative capacitors
charge negatively during negative portion of the a-c cycle, and discharge
during positive portions. In order to accomplish this, it is necessary for
the positive switching means Q21 to be zero biased into a nonconductive
mode during positive portions and forwardly biased into a conductive mode
during negative portions of the a-c cycle. Conversely, it is necessary for
the negative switching means Q22 to be zero biased into a nonconductive
mode during the negative portions and forwardly biased into a conductive
mode during the positive portions. This is accomplished using switching
control circuits such as 65 and 66 and applying the appropriately timed
control voltages across terminals E, F, G and H, as explained above.
Proper asynchronous operation of positive and negative switching
transistors Q21 and Q22 allows the positive and negative charge stored in
positive capacitors C60-C63 and negative capacitors C64-C67, to be
appropriately discharged through inductive choke L16 and lamp 409 back to
current source 401.
The initiation of discharge lamp 409 requires a boosted startup voltage to
be applied across the spaced electrodes of the lamp. Starting circuit 450
is used to provide a boosted negative voltage through switching transistor
Q22 to lamp 409. Starting circuit 450 operates in the following manner.
Switch 404 is closed upon startup and current begins to flow into the
positive and negative capacitors in an alternate fashion during positive
and negative portions of the a-c. During positive portions of current from
source 401 terminal 402 is positive with respect to terminal 403 and the
first side of capacitors C68 charges positively and the second side
thereof charges negatively, thus establishing a potential thereacross.
When the source 401 swings negative the potential across capacitor C68 is
forced thereacross thus increasing the potential differential thereacross
by the additional potential of the negative swing voltage. This increased
negative voltage on the second side of capacitor C68 flows through diode
D107 and further increases the negative charge on the first side of
capacitor C69 with respect to ground. A gate pulse is applied via D to the
gate of SCR-1 at or immediately after closing switch 404 thus closing
SCR-1 for flow of negative current from capacitor C69 through SCR-1 during
positive portions when the negative switching transistor Q22 is closed.
The anode of SCR-1 is maintained positive relative to the cathode because
of the boosted negative voltage produced by starting circuit 450. The high
negative voltage stored on capacitor C69 allows intermittent delivery of a
high voltage peak at the start of a positive portion of the alternating
current which precedes discharge of capacitors C64-C67 because of the more
negative potential existing on C69. This increased negative voltage allows
arcing to occur across the electrodes of the discharge lamp 409, thus
starting operation thereof.
Jumper A-5 is connected with some configurations, thus allowing small
amounts of charge to be drawn from capacitors C65 and C64 (if connected)
to the second side of C68. The use of jumper Z similarly allows negative
charge to pass through diode D106 to the second side of C68 during
positive portions of the alternating current.
Table IV presents preferred values of resistance, inductance, and
capacitance for resistors, inductors, and capacitors useful in a preferred
form of circuit 400.
TABLE IV
______________________________________
RESISTORS
FR3 .1 ohm
R70 .22 ohm
R71 .22 ohm
CAPACITORS
C60, C63, C64, C67 15 microfarads
C61, C62, C65, C66 150 microfarads
C68 30 microfarads
C69 10 microfarads
INDUCTORS
L16 5 millihenries
______________________________________
FIG. 8 shows a portion of a further preferred embodiment circuit 500
according to this invention. Circuit 500 is useful for controlling the
amount of power supplied to the main positive and negative charge storage
capacitors such as capacitors C1 and C2 of ballast and starting circuit
100 shown in FIGS. 2, 3 and 4. Circuit 500 regulates the power to such
capacitors in order to prevent excessive current flow during startup to
thereby preclude overheating of positive and negative switching means such
as Q1 and Q2.
Switching regulator circuit 500 and equivalents thereof can be used in
conjunction with a range of ballast circuits according to this invention.
Circuit 500 is designed specifically to be used in conjunction with
ballast circuits 100 and 200 described herein. The following description
of circuit 500 will explain the application of circuit 500 with circuit
100. Similar application to ballast circuit 200 and other ballast circuits
according to this invention will be readily apparent therefrom to one of
ordinary skill in the art.
Regulator circuit 500 includes a power supply subcircuit 510 which is used
to generate positive and negative direct current voltage supplies used by
operational amplifiers such as A1 and A2 in circuit 100 of FIG. 4 and A3
and A4 of circuit 500. Power supply subcircuit 510 can be of a variety of
constructions well known in the art of direct current power supplies.
A preferred form of circuit 510 advantageously employs a induction coil L17
which can advantageously be part of transformer 101 and share core 69.
Alternatively induction coil L17 can be independent from other
transformers used in the circuit. The primary side coil L5 of transformer
101 induces magnetic flux in core 69 which induces an alternating current
in coil L17. A center tap 511 of coil L17 is preferably connected to the
control ground or reference potential which is advantageously the same as
the potential existing at the output of surge resistor FR1 of FIG. 2. Such
control reference potential is indicated in the drawings by the letter C
which is also similarly used in FIGS. 2-5.
One output from coil L17 is at terminal L17a which is connected to the
anode of blocking diode D110 and to the cathode of blocking diode D113.
The opposite terminal L17b is connected to the anode of blocking diode
D111 and to the cathode of blocking diode D112. Diodes D110 and D111 allow
positive current to flow therethrough from either side L17a or L17b of
coil L17. Similarly, diodes D112 and D113 allow negative current to flow
therethrough from either side of coil L17. Capacitors C71 and C72 smooth
the resulting varying voltage passed through diodes D110-D113 to provide a
suitably stable positive and negative direct current power supply at
terminals 513 and 514, respectively.
Circuit 500 also includes a detection subcircuit 520 used to detect when
current through switching transistors Q1 and Q2 exceeds a desirable level.
Subcircuit 520 has a node 521 which is connected to the emitters of
parallel positive switching transistors Q1. Connection of node 521 to the
emitters of transistors Q2 obviates the need for using resistors R1 of
FIG. 2, instead using resistor R80. Similarly, resistors R2 of FIG. 2 can
be omitted from connection to the emitters of transistors Q2 because of
resistance being provided by resistor R81. Resistors R80 and R81 provide a
voltage differential between nodes 521, 522 and node 523 which is
connected to lamp 32 either directly or preferably through choke L1.
Subcircuit 520 further includes resistor R82 which is connected at a first
end thereof to node 521, and at a second end thereof to a first side of
capacitor C70. The second side of capacitor C70 is connected to node 522.
An optical isolator switching means such as photo-triac PT1 having a light
emitting diode portion LED3 is connected in parallel with capacitor C70.
Light emitting diode LED3 beams onto the photosensitive triac T3 causing
it to close into a conductive mode when LED3 is provided with a sufficient
minimum voltage thereacross to produce illumination.
Detection subcircuit 520 operates in the following manner. Current flows
through switching transistors Q1 and Q2 as explained above with regard to
ballast circuit 100. Positive current passing from the emitters of
positive transistors Q1 is conducted through resistor R80 and to lamp 32.
Similarly, negative current flows from the collectors of switching
transistors Q2 through resistor R81 to lamp 32. With either positive or
negative current flow there is a voltage drop across R80 or R81,
respectively. The voltage drop across resistors R80 and R81 is derectly
proportional to the current flowing therethrough. During normal operation
the current flowing through resistor R82 is not sufficient to create a
voltage differential across capacitor C70 and LED3 which is sufficient to
illiminate LED3. During periods of high current demand, such as at
startup, then a sufficient voltage differential is developed across LED3
thereby causing it to illuminate and close triac T3 into a conductive
mode. Triac T3, as part of phototriac PT1, controls the application of the
voltage of node 560 to remaining portions of the circuit, which will now
be described.
Circuit 500 further includes resistor R83 connected at a first end to the
first side L17a of coil L17. The second end of resistor R83 is connected
to the anode of photo-triac PT1. The cathode of photo-triac PT1 is
connected to conductor C. A resistor R84 is also connected to the output
of phototriac PT1 at one end. The other end of resistor R84 is connected
to the cathode of blocking diode D114, and the anode of blocking diode
D115. The cathode of blocking diode D114 is connected to the plus input of
a comparative operational amplifier A3. The anode of diode D114 is also
connected to the first side of capacitor C73 and the first side of
resistor R86. The second sides of capacitor C73 and resistor R86 are
connected to conductor C. The minus input of operational amplifier A3 is
connected to a second end of resistor R85 and to a first end of resistor
R88. The first end of resistor R85 is connected to the second side L17b of
coil L17. The second end of resistor R88 is connected to conductor C.
The cathode of diode D115 is connected to the plus input of comparative
operational amplifier A4. The cathode of diode D115 is further connected
to the first side of capacitor C74 and resistor R87. The second sides of
capacitor C74 and resistor R87 are connected to conductor C. The minus
input of operational amplifier A4 is also connected to the second end of
resistor R85 and the first end of resistor R88. Resistor R85 and R88
effectively divide the voltage between second side L17b and conductor C
for use as a sinusoidal or other varying voltage against which the plus
inputs of amplifiers A3 and A4 are compared.
The output from amplifier A3 is connected to one end of resistor R90. The
opposite end of resistor R90 is connected to the cathode of blocking diode
D116. The anode of blocking diode D116 is connected to the base of a PNP
type control transistor Q23. The anode of blocking diode D116 is also
connected to a first end of resistor R91 and the cathode of blocking diode
D118. The second end of resistor R91 is connected to conductor C. The
anode of diode D118 is connected in series with two other blocking diodes
D119 and D120, with the anode of diode D120 being connected to conductor
C.
The output of operational amplifier A4 is connected to an arrangement of
components conceptually similar to that just described with respect to
amplifier A3. The output of amplifier A4 is connected to one end of
resistor R89. The other end of resistor R89 is connected to the anode of
blocking diode D117. The cathode of diode D117 is connected to the base of
NPN control transistor Q24. The cathode of diode D117 is also connected to
one end of resistor R92 and to the anode of blocking diode D123. The
opposite side of resistor R92 is connected to conductor C. The cathode of
diode D123 is connected in series with two other blocking diodes D122 and
and D121, which are oriented with their anodes toward the base of
transistor Q24. The cathode of diode D121 is connected to conductor C.
The emitters of control transistors Q23 and Q24 are connected to the bases
of regulator transistors Q25 and Q26, respectively. Resistors R93 and R94
are connected between the emitters of transistors Q23 and Q24,
respectively, and conductor C. The collector of transistor Q23 is
connected to conductor 540 which is connected to the anode of diode D1 of
FIG. 2. The collector of transistor Q25 is also connected to conductor
540. The collectors of transistors Q24 and Q26 are connected to the
cathode of diode D2 via conductor 550. The emitters of transistors Q25 and
Q26 are connected to conductor C via resistors R95 and R96, respectively.
Resistors R97 and R98 are connected between conductor C and conductors 540
and 550, respectively.
The operation of circuit 500 will now be explained more fully. The
functions of circuit 500 are primarily to detect when excessive current is
being supplied to switching transistors Q1 and Q2 (FIG. 2) and then to
control the percentage of time during which each of the positive and
negative cycle portions are allowed to charge the main positive and
negative capacitors C1 and C2. Transistors Q25 and Q26 are the switching
elements which control the primary flow of current from conductor C
therethrough, and supply the rectifying diodes D1 and D2. The percentage
of time that current is supplied controls the resulting charge on
capacitors C1 and C2 thus regulating the current discharged through main
switching transistors Q1 and Q2. Regulation of the current flow through
transistors Q1 and Q2 allows operation without excessive heat, thus
extending the service life and reliability of the ballast circuits.
Detection of the current flow through transistors Q1 and Q2 is performed by
detection subcircuit 520 as explained above. Detection circuit 520 not
only detects excessive current but further provides a control signal
during times of excess current which causes the control potential provided
by first side L17a of coil 17 to be shunted to control ground, conductor
C, through phototriac PT1. This shunting of control potential to the
control ground or reference potential, controls the rectified voltage
input to the plus terminal of amplifiers A3 and A4. The output from
amplifiers A3 and A4 operates in the following manner.
During negative portions of alternating current the control coil L17
produces power which is passed through diode D114 to the plus or
noninverting input of amplifier A3. Capacitor C73 smooth the negative
signal passing through diode D114 rendering it essentially direct current.
Resistor R86 allows some current leakage to control ground (conductor C)
so that increases and decreases in the potential at node 560 result in
suitably quick response (1 second) by amplifier A3.
Amplifier A3 provides a negative output signal when the inverting input
voltage exceeds the noninverting input voltage. During normal operation
the inverting (-) input is less negative and thus exceeds the plus input
to produce a -8 volt output to diode D116. This biases transistors Q23 and
Q25 into a conductive mode allowing full power to reach the positive main
capacitor C1.
If power is excessive then triac T3 is closed during a portion of the cycle
and the potential at node 560 goes to control ground. The potential at the
noninverting input thus increases becoming less negative and approaches
control ground as capacitor C73 discharges through resistor R86. The
potential on the inverting input of amplifier A3 varies positive and
negative. When the alternating potential at the inverting input falls
below the reduced negative potential of the noninverting input, then the
output from amplifier A3 goes positive thus removing the biasing voltage
to transistors Q23 and Q25 thereby placing them in a nonconductive mode.
This terminates power to the main positive capacitor C1, thereby reducing
the charge placed thereon and the power conducted through switching
transistors Q1.
The operation of amplifier A4 and transistors Q24 and Q26 is essentially
the same as the description just given with respect to amplifier A3 and
transistors Q23 and Q25, except that the output from amplifier A4 is
normally positive because the plus terminal is held at a higher positive
voltage than the varying voltage at the minus terminal. This positive
output biases transistors Q24 and Q26 closed providing full power to
negative main capacitor C2. When phototriac PT1 closes it decreases so
that the varying voltage at the minus input exceeds the voltage at the
plus input during part of the negative cycle. This causes the output of A4
to go negative thereby removing the forward bias on transistors Q24 and
Q26. The power supplied to negative main capacitor C2 and switching
transistors Q2 is thus reduced. Transistor Q26 controls flow of negative
current from conductor C to the cathode of rectifying diode D2.
Regulating circuit 500 thus controls current flow to both positive and
negative main capacitors C1 and C2 in order to maintain a predetermined
current flow through switching transistors Q1 and Q2.
Table V below presents preferred values of resistance and capacitance for
resistors and capacitors useful in a preferred form of circuit 500.
TABLE V
______________________________________
RESISTORS
R80, R81 0.25 ohms
R82 12 ohms
R83 2.2K ohms
R84 4.7M ohms
R85 22K ohms
R86 10M ohms
R87 10M ohms
R88 10K ohms
R89, R90 330 ohms
R91, R92 10K ohms
R93, R94 1K ohms
R95, R96 0.035 ohms
R97, R98 100K ohms
CAPACITORS
C70 50 microfarads
C71, C72 1000 microfarads
C73, C74 0.1 microfarads
______________________________________
FIG. 9 shows a further alternative embodiment of electronic ballast 600
according to this invention. Ballast 600, as shown, is adapted for use
with 400 watt metal halide lamps, although the concepts described are
useful for most, if not all, types of discharge lamps. Ballast circuitry
600 receives electrical current from an alternating current (AC) source
601. The preferred current source is a nominal 120 volt rms AC current
such as widely used in the United States. First current source connection
node 602 represents the voltage-varying side of the alternating current
source and second current source connection node or terminal 603
represents the neutral or common side of the alternating current source.
The first, voltage-varying current supply conductors are designated with
the letter M in the drawings. The second, neutral or common side current
supply conductors connected to terminal 603. of the AC source are
designated with the lettr N.
Current from electricity source 601 flows to a dual polarity AC-DC
converter 610. AC-DC converter 610 can be of a variety of different
designs which provide a positive current source terminal 611 and a
negative current source terminal 612. In the preferred embodiment positive
current source 611 provides approximately +170 volts DC in the no load
condition. The negative current source terminal 612 provides approximately
-170 volts in the no load condition. The positive and negative current
supplied from terminals 611 and 612 are substantially direct current with
some variation possible due to discharge of capacitors or other energy
storage device used in the AC-DC converter.
The positive output 611 from converter 610 is communicated to a positive
modulation subcircuit which can advantageously be in the form of a DC-DC
converter 620. The negative current output 612 is similarly connected to a
negative modulation subcircuit which can advantageously also be in the
form of a DC-DC converter 630.
The positive modulator advantageously includes a current modulating element
such as a transistor, specifically, field effect transistor (FET) 621. The
positive current modulating transistor 621 is controlled by a positive
modulator drive subcircuit 622. An inductor 661 can be utilized as a choke
or filtering device which smooths the modulated positive power which is
controllably passed by modulation transistor 621. The resulting current
flow from inductor 661 is communicated through a diode 642 to the
collector of positive lamp discharge switching means Q103. Transistor or
other switching means Q103 is controlled using a positive lamp discharge
switching control circuit 660. A positive current output terminal such as
the emitter of transistor Q103 is connected to a supply side of discharge
lamp 700, preferably using a relatively low value resistance indicated by
R204.
FIG. 9 also shows a positive high voltage arc initiation circuitry 640. Arc
initiation circuitry 640 is connected to receive line AC to provide power
thereto. Other sources of power may also be possible, such as output 611.
Circuitry 640 generates a relatively high voltage and stores it unitl an
appropriate time during the discharge of positive current through
discharge lamp 700. The amount of current provided by positive arc
initiation circuitry 640 is preferably made sufficient to initiate
discharge within lamp 700 through diode 641, transistor Q103 and resistor
R204. The energy storage capability of arc initiation circuitry 640 is
also preferably made relatively low so that the higher voltage power
source is only utilized for a brief portion of a positive lamp discharge
period associated with discharge of positive current through lamp 700.
This minimizes the energy expended and makes the ballast more efficient.
Negative current from negative output terminal 612 is communicated to a
negative current modulator, such as at field effect transistor 631 which
acts as a negative modulating element. The negative modulating element is
controlled using negative modulator drive subcircuit 632. The current
output from modulation transistor 631 is also preferably conducted through
an inductive choke 662 to help filter the modulated current and to help
regulate current flow therethrough. The negative current output from
inductor 662 is conducted through diode 652 and resistor R205 to a
negative lamp discharge switching means Q104. Current is controllably
conducted through the negative lamp discharge switch Q104 to discharge
lamp 700. The negative lamp discharge switching means is controlled using
a negative lamp discharge switching control subcircuit 670.
The negative side or channel of circuitry 600 is also provided with a
negative high voltage arc initiation subcircuit 650. Negative arc
initiation circuitry 650 functions in a manner similar to that described
above with respect to the positive arc initiation circuitry 640. The
relatively high voltage negative current produced by circuitry 650 is
passed through diode 651, resistor R205 and negative lamp discharge
switching means Q104 to produce a brief relatively more negative discharge
through lamp 700.
FIG. 10 shows a portion of circuitry 600 in greater detail than shown in
the abbreviated block/schematic diagram presented in FIG. 9. FIG. 10 shows
the voltage-varying line current being supplied at terminal M. Positive
and negative current supplied thereto is effectively divided into positive
and negative components by diodes 613 and 614, respectively. Positive side
diode 613 is connected with the anode towards the alternating current
source conductor M. Negative diode 614 is connected with the cathode
thereof connected to the incoming line voltage via conductor M. The
cathode of positive diode 613 is connected to a positive converter storage
capacitor C100. The other side of capacitor C100 is connected to the
neutral conductor N. Similarly, the anode of negative diode 614 is
connected to one side of a main negative converter capacitor C101. The
other side of capacitor C101 is connected to the neutral line N.
Capacitors C100 and C101 are connected across their terminals using
resistors R200 and R201, respectively, for slowly discharging these
capacitors when power is turned off. The voltage produced at the first
side of capacitor C100 and on conductor 617 is substantially DC positive
current made available to remaining portions of the positive side of the
electronic ballast 600. The negative substantially DC current developed on
conductor 618 is similarly used to supply negative current to remaining
portions of the negative side or channel of circuit 600.
Positive DC conductor 617 is connected to the drain connection of
transistor 621. The gate of transistor 621 is connected to the positive
modulator drive circuitry 622. The source connection of transistor 621 is
also connected to drive circuitry 622. In an analogous manner, negative
current conductor 618 is connected to the source connection of negative
modulator transistor 631. The gate of transistor 631 is connected to the
negative modulator drive circuitry 632. The negative modulator drive
circuitry 632 is also connected to the source connection of transistor
631. The drain connection of transistor 631 functions as a current output
terminal for the modulator and is connected to remaining portions of the
circuitry to supply the primary power for discharge to lamp 700. The
source connection of transistor 621 is similarly used as an output for the
positive modulator to provide the primary positive current for discharge
through lamp 700. The modulated current from transistors 621 and 631 is
preferably in the form of pulse width modulated pulses of positive and
negative current, respectively. These modulation transistors are
preferably turned fully on and fully off in order to minimize power
dissipation during modulation of the positive and negative currents.
The positive output of the current modulator is connected to one end of
inductor 661 and to the cathode of diode D200. The other end of inductor
661 is connected to resistor R202. The other end of resistor R202 is
connected to one side of capacitor C102 and to the anode of diode 642. The
other side of capacitor C102 is connected to the anode of diode D200 and
to the neutral line N. The cathode of diode 642 is connected to one side
of capacitor C104 and to the positive lamp discharge switching transistors
Q103, such as at the collectors of parallel bipolar transistors Q103a and
Q103b. The other side of capacitor C104 is connected to the neutral
conductor N. The emitters of positive lamp discharge transistors Q103a and
Q103b are connected to resistors R204a and R204b, respectively. The other
ends of resistors R204a and R204b are connected to the supply side of
discharge lamp 700. The bases of positive switching means Q103 are
connected via conductor AA to a suitable positive lamp discharge switching
control circuit 660, such as shown in FIG. 11 and described hereinafter.
Modulated negative current from negative modulator transistor 631 is
connected to one end of inductor 662 which acts as a filtering and energy
storage device for taking the pulse modulated current and converting it
back into a substantially DC signal at the opposite or output end thereof.
The output end of inductor 662 is connected to resistor R203. The other
end of resistor R203 is connected to the cathode of diode 652 and to one
side of capacitor C103. The other side of capacitor C103 is connected to
the neutral line N. The anode of diode 652 is connected to one side of
capacitor C105 and to parallel resistors R205a and R205b. Negative current
is conducted through resistors R205a and b as controlled by the negative
lamp discharge switching means which is preferably in the form of parallel
bipolar transistors Q104a and Q104b. Transistors Q104a and b are connected
with the emitters thereof to ends of resistors R205a and R205b,
respectively. The collectors of transistors Q104a and Q104b are connected
together and to the supply side of discharge lamp 700. The bases of
transistors Q104a and b are connected through conductor BB to a negative
lamp discharge switching control subcircuit 670 which is shown in greater
detail in FIG. 11 and described hereinafter.
The supply and neutral terminals of discharge lamp 700 are preferably
connected across using a suitable excess voltage protection device such as
a transzorb having zener diodes 708 and 709. Zener diode 708 is connected
with the anode thereof to the supply side of discharge lamp 700 and the
cathode thereof connected to the cathode of zener diode 709. The anode of
zener diode 709 is connected to the neutral side of lamp 700.
FIG. 10 also shows the positive high voltage arc initiation circuitry 640
near the top thereof. Circuitry 640 is connected to the incoming line
voltage M using a first side of capacitor C108. The second side of
capacitor C108 is connected to the cathode of diode 645. The anode of
diode 645 is connected to the neutral conductor N of the alternating
current source. A resistor R207 is connected across capacitor C108 to
allow slow discharge when power is terminated. The second side of
capacitor C108 and the cathode of diode 645 are connected to the anode of
diode 641. The cathode of diode 641 is connected to the cathode of diode
642 and to the collectors of the positive lamp discharge transistors Q103.
FIG. 10 also shows the negative high voltage arc initiation circuitry 650.
Circuitry 650 includes capacitor C109 which has the first side thereof
connected to the incoming voltage-varying line conductor M. The second
side of capacitor C109 is connected to the anode of diode 655. The cathode
of diode 655 is connected to the neutral line conductor N. Resistor R206
is connected across capacitor C109 to allow slow discharge when power is
terminated. The second side of capacitor C109 is connected to the cathode
of diode 651. The anode of diode 651 is connected to the anode of diode
652 and to negative lamp discharge switching transistors Q104 via
resistors R205a and R205b.
The basic flow of positive and negative current used to power lamp 700 will
now be described. During positive portions of the alternating current
cycle of electricity source 601 current flows through diode 613 and is
stored in capacitor C100. A number of cycles of positive current causes
capacitor C100 to become sufficiently charged so as to supply a somewhat
fluctuating but substantially DC positive current along conductor 617.
Current is modulated through modulator transistor 621 while applying a
voltage to the gate of transistor 621 which is sufficient to forwardly
bias the transistor relative to the voltage applied at the source of
transistor 621. This modulation control signal preferably turns the
modulation transistor on and off at a frequency which is substantially
greater than the operating frequency of the incoming line current.
Preferably the frequency of the modulator is 10 or more times greater than
the frequency of the incoming line current and the frequency of the
alternating current supplied by the ballast to the discharge lamp. In the
preferred embodiment shown the modulating transistor 621 operates at a
frequency of approximately 100 KHz.
The modulated current is supplied in the form of DC pulses of brief
duration which are conducted through inductor 661 to provide a modulated
substantially DC output therefrom. The primary positive lamp discharge
current passed through inductor 661 is also conducted through current
sensing resistor R202 in order to provide a voltage differential
thereacross which is used in control of the modulation circuitry using
conductors P and Q.
Inductor 661, capacitor C102 and diode D200 form a current regulating,
filtering and secondary energy storing function within the circuit. When
positive lamp discharge switches Q103 are conductive, current flows
through inductor 661 resistor R202 in a surge with substantially constant
DC values being produced through diode 642. However, when switches Q103
are turned off, inductor 661 tends to continue conducting current as the
magnetic field collapses thus drawing positive current through diode D200
from the neutral side of capacitor C102. The current flowing through diode
D200 and inductor 661 passes through resistor R202 to the first side of
capacitor C102. While lamp discharge transistors Q103 are turned off, the
modulation transistor 661 continues to pulse reduced amounts of current
therethrough in order to fully charge the energy storing and filtering
circuit formed by inductor 661, capacitor C102 and diode D200 to the full
DC voltage of capacitor C100, approximate +170 volts. This allows the
circuitry to be in a fully charged condition and ready for discharge when
the positive lamp discharge transistors Q103 are turned on for the next
surge of positive current through discharge lamp 700.
In the preferred embodiment shown the positive discharge transistors Q103
are turned on during positive portions of the line alternating current.
The positive lamp discharge period defined by transistors Q103 being
conductive is substantially coextensive with the positive portions of the
AC cycle in the preferred embodiment. Relatively minor amounts of dead
band time are preferably provided at the start of the positive portion of
the line AC cycle and at the end of the positive portion of the line AC
cycle in order to assure that there is no simultaneous conduction through
the positive and negative lamp discharge transistors Q103 and Q104 and
maintain their asynchronous operation. During positive lamp discharge
periods substantially all current through lamp 700 is controlled by the
positive lamp discharge transistors Q103. The substantially in-phase
operation of positive lamp discharge transistors Q103 with respect to the
line alternating current cycles is not necessary but is advantageous.
The operation of the high voltage generating circuit 640 used for arc
initiation will now be described. During a negative portion of line AC
positive current is conducted from the neutral conductor N through diode
645 and on to the second side of capacitor C108. When the line AC current
swings positive, the positive potential on the first side of capacitor
C108 causes an increase in the voltage on the second side of C108 because
the voltage across the capacitor tends to be maintained. In no load
conditions the voltage is doubled. In loaded conditions the charge
generated and stored on the second side of capacitor C108 is discharged
through diode 641 for a brief portion of the lamp discharge cycle until
the capacitor C108 is discharged to a point where the anode of diode 641
is at approximately the same voltage as the anode of diode 642. At that
point conduction of the primary lamp operating current during the positive
lamp discharge periods is provided by the modulated current flow passing
through diode 642. The positive arc initiation circuitry 640 provides a
relatively short duration flow of higher voltage current which is
efficient for initiation of lamp discharge without requiring generation of
high voltage current for all of the current used to power the discharge
lamp.
Negative current flows from conductor M to lamp 700 in a manner
substantially the same as described above with respect to the positive
side. Specifically, negative current flow through diode 614 during the
negative potential portions of the line alternating current provided on
conductor M. The negative charge passed by diode 614 is stored on the
first side of capacitor C101. The current modulating switch or gate 631
pulses the substantially DC current provided by conductor 618. The pulsed
modulated current from gate 631 is conducted to inductor 662. Inductor
662, capacitor C103 and diode D201 provide the same filtering and energy
storing function as described above with respect to positive inductor 661,
capacitor C102 and diode D200 with opposite polarity. The primary negative
operating current passes through inductor 661, resistor R203 and diode 652
when negative lamp discharge switching transistors Q104 are turned on.
Transistors Q104 are controlled by suitable biasing voltage via conductor
BB using the negative lamp discharge switching control circuitry 670. Lamp
discharge switches Q104 controllably discharge negative current through
lamp 700. The discharge of negative current through lamp 700 occurs in
asnynchronous relationship to the discharge of positive current using lamp
discharge switches Q103, that is, the positive and negative transistors
Q103 and Q104 are not conductive at the same time. The negative current
discharge through lamp 700, as shown, advantageously occurs during the
negative potential portions of the incoming line alternating current. The
negative lamp discharge periods defined by switches Q104 being turned on
is preferably substantially coextensive with the negative potential
portions of the line current in the preferred embodiment. During negative
lamp discharge periods substantially all current through lamp 700 is
controlled by the negative lamp discharge transistors Q104. Dead band
space at the start and end of the negative lamp discharge period are also
preferably provided to assure that no simultaneous conduction occurs
through positive and negative lamp discharge switches Q103 and Q104.
Capacitors C104 and C105 serve to reduce noise at the collectors of
transistors Q103 and Q104, respectively, due to the relatively high
impedances which exist at on conductors X and Y.
Although operation of the invention has been described above with respect
to the positive lamp discharge periods being substantially coincident with
the line AC positive potential portions and the negative lamp discharge
periods being substantially coincident with the negative potential
portions of the line current, such is not necessarily required. It is
alternatively possible that the lamp operate at frequencies different from
the line using switching transistor control circuitry which is suitably
adapted. Other variations in frequency and relationship of the discharge
lamp operating phase with respect to the phase of the incoming line
current are also possible so long as the asynchronous operation is
maintained between the positive and negative lamp discharge switching
means Q103 and Q104, respectively.
The above descriptions give a general explanation of the flow of primary
and arc initiating boosting current through the positive and negative
current flow channels of the circuit 600. Discussion will now turn to the
structural interrelationship of the driving circuits 660 and 670 used to
control the positive and negative lamp discharge switches Q103 and Q104.
FIG. 11 also shows the positive and negative lamp discharge switching means
Q103 and Q104, respectively, for ease of description and consideration.
Positive power is supplied to the collectors of switching means Q103 via
conductor X and negative current is supplied to the emitters of negative
switching means Q104 via conductor Y through resistors R205a and b. The
bases of positive lamp discharge switching transistors Q103 are connected
to the positive lamp discharge switching control or driving circuitry 660.
The bases of negative lamp discharge switching transistors Q104 are
connected to the negative lamp discharge switching control circuitry 670.
FIG. 11 further shows a power supply subcircuit 680 which is used to
generate appropriate voltages on conductors marked T and U. The conductor
marked Z is connected directly to the supply terminal 700a of lamp 700.
The lamp neutral terminal is 700b.
Circuitry 660 includes a suitable transformer 760 which includes a primary
coil L20 and a secondary coil L21. The first side of primary coil L20 is
connected to the neutral conductor N and the second side of the coil L20
is connected to hot lead M. The secondary coil L21 steps the voltage down
to approximately .+-.8 volts when the primary coil is exposed to .+-.170
volts. The first side of secondary coil 21 is connected to conductor Z
which is connected to the supply side 700a of discharge lamp 700. The
second end of coil L21 is connected to the anode of diode 761 and other
components. The cathode of diode 761 is connected to the cathode of diode
762 and to first ends of resistors R210, R212 and R213. The opposite end
of resistor R210 is connected to the first side of capacitor C120 and to
an end of resistor R211. The anode of diode 762 is also connected to the
first side of capacitor C120. The other side of capacitor C120 is
connected to conductor Z. The other end of resistor R211 is connected to
the collector of transistor 774. The base of transistor 774 is connected
to resistor R214 with the opposite end of resistor R214 connected to the
second end of coil L21. The base of transistor 774 is also connected to
the cathode of diode 763 and the anode thereof is connected to conductor
Z. The emitter of transistor 774 is also connected to conductor Z. The
collector of transistor 774 is also connected to the emitter of PNP
transistor 770. The collector of transistor 770 is connected to one end of
resistor R215 and to the base of transistor 772. The opposite end of
resistor 215 is connected to the emitter of transistor 772 and also to one
end of resistor R216 and to one side of capacitor C121. The opposite side
of capacitor C121 is connected to conductor Z. The opposite end of
resistor R216 is connected to the anode of diode 764 which has the cathode
thereof connected to the second end of coil L21. The second end of coil
L21 is also connected to resistor R217. The opposite end of resistor R217
is connected to the base of transistor 773 and to one end of resistor
R219. The opposite end of resistor R219 is connected to conductor Z. The
collector of transistor 773 is connected to conductor Z. The emitter of
transistor 773 is connected to the cathode of diode 765. The anode of
diode 765 is connected to the collector of transistor 772, the base of
transistor 771, and to the cathode of diode 766. The base of transistor
771 is also connected to the second end of resistor R212. The collector of
transistor 771 is connected to the second end of resistor R213 and the
emitter of transistor 771 is connected to the anode of diode 766. The
emitter of transistor 771 is also connected to a first side of resistor
R218. The second end of resistor R218 is connected to conductor Z. The
emitter of transistor 771 is further connected to a first side of
capacitor C122 and to the bases of positive lamp discharge switching
transistors Q103a and b. The base node for such transistors has been
designated conductor AA which refers to the signal which drives the bases
of these positive switching transistors. This designation is used merely
for convenience in relating FIGS. 10 and 11.
The positive lamp discharge switching control circuitry 660 operates in the
following manner. During positive portions of the incoming line current, a
positive voltage is generated on the second side of coil L21. This
positive voltage is referenced with respect to the first side of coil L21
which is connected to the voltage which is experienced on the supply side
of the discharge lamp being powered. Thus the signal generated in coil L21
is superimposed on the alternating voltage existing on the supply side of
the lamp. The relatively more positive voltage generated on the second
side of L21 during positive portions of line current applies a relatively
higher voltage to the base of transistor 774 than to the emitter thereof
which is connected to Z which is effectively a control ground. This turns
transistor 774 on causing conduction through diode 761, resistor R210 and
R211 to the collector of transistor 774 and on to conductor Z. The voltage
generated at the node between resistors R210 and R211 is used to charge
the first side of capacitor C120. Capacitor C120 is used to apply a
minimum voltage of relatively DC current through diode 762 to the first
sides of resistor R212 and R213. The conductive state of transistor 774
during the positive portion of the line cycle causes the emitter of
transistor 770 to be pulled low thus turning transistor 770 off. This in
turn causes the base and emitter of transistor 772 to reach a relatively
equal voltage turning transistor 772 off.
The base of transistor 773 is forward biased during positive portions of
line current thus drawing current through resistor R212 which forward
biases the base-emitter junction of transistor 771. This causes transistor
771 to turn on thus conducting current through resistor R213 to the bases
of the positive lamp discharge switching transistors Q103a and b. The base
voltage at conductor AA increases and decreases during the positive cycle
in a substantially sinusoidal manner. The current through switching means
Q103 is also substantially sinusoidal during the positive lamp discharge
period. The positive lamp discharge period is approximately from 5.degree.
until 175.degree. of the 180.degree. positive line half cycle.
During the negative cycle of line current transistor 774 is turned off.
This causes a relatively higher voltage to be applied from capacitor C120
through resistor R211 to the emitter of PNP transistor 770 thus turning it
on. When transistor 770 turns on, a relatively higher voltage is applied
to the base of transistor 772 as compared to the emitter thereof thus
turning transistor 772 on. Diode 764 and capacitor C121 effectively form a
peak detector which is negative in voltage at approximately -4 volts
relative to Z. When transistor 772 turns on, this negative voltage is
conducted through transistor 772 from emitter to collector and through
diode 766 to affirmatively bias the base of the main lamp discharge
switching transistors Q103 into a reverse biased condition across the
base-emitter junction. This reverse biased condition assures that the
transistors are turned off and that positive current cannot be connected
to the supply side of lamp 700 during negative lamp discharge periods.
The negative lamp discharge switching control circuitry 670 is constructed
and operates in an analogous fashion to the positive circuitry 660 just
described. Circuitry 670 includes a transformer 780 which has a primary
coil L22 and a secondary coil L23. The first side of coil L22 is connected
to neutral conductor N and the second side is connected to the voltage
varying conductor M. The first side of coil L23 is connected to the
cathode of diode 781 and other components. The second side of coil L23 is
connected to conductor Y which is effectively used as the control ground
for the negative lamp discharge switching control circuitry 670. The first
side of coil L23 is also connected to one side of resistor R224, the other
end of which is connected to the base of transistor 794. The base of
transistor 794 is also connected to the cathode of diode 783 which has an
anode connected to conductor Y. The emitter of transistor 794 is connected
to conductor Y. The cathode of diode 781 is connected to one end of
resistor R220. The other end of resistor R220 is connected to one end of
resistor R221. The other end of resistor R221 is connected to the
collector of transistor 794. A first side of capacitor C130 is connected
to the node between resistors R220 and R221 and also connected to the
anode of diode 782. The cathode of diode 782 is connected to the cathode
of diode 781 and to first ends of resistors R220, R222 and R223. The
second side of capacitor C130 is connected to conductor Y. The collector
of transistor 794 is also connected to the emitter of PNP transistor 790.
The base of transistor 790 is connected to conductor Y and the collector
thereof is connected to the base of transistor 792. Resistor R225 extends
between the emitter of transistor 792 and the collector of transistor 790.
The emitter of transsistor 792 is also connected to the first side of
capacitor C131, the other side of which is connected to conductor Y. The
first side of capacitor C131 is connected to one end of resistor R226 and
the other end of that resistor is connected to the anode of diode 784. The
cathode of diode 784 is connected to the first side of coil L23. The
collector of transistor 792 is connected to the base of transistor 791 and
to the anode of diode 785 and cathode of diode 786. The cathode of diode
785 is connected to the emitter of PNP transistor 793. The base of
transistor 793 is connected via resistor R227 to the first side of coil
L23. Resistor R229 is connected between the base of transistor 793 and
conductor Y. The collector transistor 793 is connected to conductor Y. The
collector of transistor 791 is connected to a second side of resistor
R223. The emitter of transistor 791 is connected to the bases of negative
lamp discharge transistors Q104, the anode of diode 786, and one side of
resistor R228. The other side of resistor R228 is connected to conductor
Y. A capacitor C132 is connected between the bases of the negative lamp
discharge switching transistors Q104a and b and conductor Y. Conductor BB
represents the negative lamp discharge switching control circuitry output
signal to the negative lamp discharge switching means Q104.
In operation the negative lamp discharge switching control circuitry 670
generates a relatively more positive voltage at the first end of coil L23
during the negative cycle portions of the incoming line current. The
circuit otherwise operates in the manner described above with respect to
positive circuit 660 except that it is of opposite polarity and out of
phase in operation because of the opposite relationship between primary
and secondary coils L22 and L23 of transformer 780. This results in the
base conductor BB being forward biased in a substantially sinusoidal
fashion during the negative portion of the incoming line alternating
current cycle. It also results in a reverse bias on the base-emitter
junction of transistors Q104a and b during the positive cycle portions of
the incoming line current.
Control circuits 660 and 670 provide for asynchronous operation of the
positive and negative lamp discharge switching means Q103 and Q104. In the
preferred embodiment as shown the positive lamp discharge switching
transistors Q103 are conductive during the positive portion of the AC line
cycle. The negative lamp discharge switching transistors Q104 are biased
into a conductive mode during the negative portion of the incoming line AC
current. Although this in-phase relationship is preferred in the
embodiment as shown and described, it is alternatively possible to operate
the lamp discharge transistors partially out of phase or directly out of
phase with the incoming line alternating current cycles. However, the
positive and negative lamp discharge switching means Q103 and Q104 must be
operated asynchronously or otherwise be adapted to prevent application of
the positive and negative currents to lamp 700 at the same time.
FIG. 11 also shows small power supply subcircuit 680 which includes a
resistor R230 which is connected to the second end of coil L21. The other
end of resistor R230 is connected to the anode of diode 767 and to the
cathode of diode 768. The cathode of diode 767 is connected to one side of
capacitor C123 and to one end of resistor R231. The other side of
capacitor C123 is connected to conductor Z. The other end of resistor R231
is connected to conductor T and to one end of resistor R232. The other end
of resistor R232 is connected to conductor Z. Conductor T is communicated
to the modulation circuitry shown in FIG. 12A.
In operation diode 767 allows positive current to flow therethrough and
charge capacitor C123. This provides a substantially DC voltage riding on
the alternating voltage defined by conductor Z. Conductor T provides a
substantially constant +4 volt level over the alternating voltage existing
on conductor Z which is connected to the supply side of lamp 700. The +4
volts of conductor T with respect to conductor Z defines the target
voltage differential used in the control of the positive pulse width
modulator described below.
Circuit 680 also includes a negative power supply using diode 768 which has
the cathode thereof connected to resistor R230 and the anode thereof
connected to one side of capacitor C124. The other side of capacitor C124
is connected to conductor Z. The anode of diode 768 is also connected to
one end of resistor R233. The other end of resistor R233 is connected to
conductor U and to one end of resistor R234. The other end of resistor
R234 is connected to conductor Z. This portion of the power supply
circuitry 680 generates a voltage of approximately -4 volts at conductor U
with respect to the alternating voltage existing on conductor Z. The
voltage on conductor U is utilized in the negative modulator driving
circuitry 632 described below with respect to FIG. 13A. The circuitry
generating the voltage at conductor U functions in substantially the same
manner as that described above with respect to the generator of the
voltage on conductor T except that diode 768 is oppositely oriented in
order to pass the negative portion of the alternating current generated in
coil L21 thereby leading to the -4 volt supply voltage at conductor U
versus the +4 volts supply voltage on conductor T.
FIGS. 12A and 12B show the drive circuitry for controlling operation of the
positive modulator transistor 621. The inputs to this system include the
signal T which is the target +4 differential voltage generated by
circuitry 680 with respect to the lamp supply terminal. Inputs also
include signal P which is generated at the node between inductor 661 and
current sense resistor R202. Final input is signal Q which is generated on
the other side of resistor R202. Resistor R202 is shown in FIG. 10 and the
voltage drop thereacross is indicative of the amount of current which is
being passed through inductor 661. The outputs from the system are the HH
signal and II signal which are connected to the gate and source terminals
of transistor 621 to control its pulse modulation operation. In general
the circuitry of FIGS. 12A and 12B are referenced to Q which is the
voltage at the lower voltage end of current sense resistor R205.
FIG. 12A shows the +4 volt power supply conductor T with respect to
conductor Z being connected to the circuit at one end of resistor R250 and
to an anode of diode 801. The second end of resistor 250 is connected to
resistor R251. The cathode of diode 801 is connected to the other side of
resistor R251 which is also connected to a third resistor R252. The second
end of resistor R252 is connected to resistor R253. The second end of
resistor R252 is also connected to the anode of diode 802 and cathode of
diode 803 as well as to the inverting input (-) of operational amplifier
A5 and one end of feedback resistor R254. The second end of resistor R254
is connected to the output of operational amplifier A5. The second end of
resistor R253 is connected to conductor Q which is functioning
substantially as a referenced ground and to the cathode of diode 802 and
the anode of diode 803. The inverting or plus (+) input of operational
amplifier A5 is connected to one end of resistor R255 with the opposite
end of resistor R255 being connected to conductor Q.
The resistors R250, R251, R252 and R253 are connected between the T
conductor and Q conductor to form suitable voltage drops therebetween.
Diode 801 is connected to provide protection against excessive swing in
the operational amplifier A5. Diodes 802 and 803 similarly limit the swing
of the minus input of that operational amplifier.
The error signal generator 623 also includes operational amplifier A6 which
is connected to function as a current sensing comparator. The inverting
input of operational amplifier A6 is connected to the Q conductor via
input resistor R258. The noninverting input is connected to conductor P
via input resistor R259. Thus the inputs to this operational amplifier are
connected across the current sensing resistor R202 shown in FIG. 10. The
inverting input of operational amplifier A6 is also connected to one end
of resistor R260 and one end of feedback resistor R261. The other end of
resistor R260 is connected to conductor EE which supplies an approximately
+0.7 volt reference with respect to conductor Q. The opposite end of
feedback resistor R261 is connected to the output of amplifier A6.
Amplifier A6 is also connected to conductor FF which is a +5 volt supply
with respect to conductor Q, and is generated in pulse width modulator
chip 860 shown in FIG. 12B. Operational amplifier A6 is also connected at
another power connection to an approximately -4.3 volt power supply
generated in conductor 816 by a 3.6 volt zener diode 809 connected in
series with diode 815 to conductor Q.
The output of current sensing comparator A6 is connected to the cathode of
diode 808 and the anode thereof is connected to a first end of resistor
R263. The opposite end of resistor R263 is connected to the cathode of
diode 818, the base of transistor 807, and a first end of resistor R264.
The anode of diode 818 is connected to conductor Q. The other end of
resistor R264 is connected to the cathode of zener diode 809 and the
cathode of diode 815. The anode of diode 815 is connected to conductor Q.
The collector of transistor 807 is connected to the cathode of diode 815.
The output of amplifier A5 is connected to ends of resistors R256 and R257.
The other end of resistor R257 is connected to the cathode of diode 804
and to the anode of diode 805. The cathode of diode 804 is connected to
the base of NPN transistor 806. The base of NPN transistor 806 is also
connected to resistor R262. The opposite end of resistor R262 is connected
to the +0.7 volt power supply line EE from power supply circuitry 817. The
collector of transistor 806 is also tied to the +0.7 volt supply EE. The
emitter of transistor 806 is connected to the second end of resistor R256.
Resistor R256 and the emitters of transistors 806 and 807 are connected to
the noninverting input of operational amplifier A8 via resistor R269. A
capacitor C140 is connected between the emitter of transistors 806 and 807
and conductor Q to suppress high frequency noise. The signal generated at
the node marked 819 connected to the second end of resistor R256 and the
emitters of the transistors 806 and 807 defines the output from the inner
signal generator 623. This output is received by the integrator circuitry
624.
The error signal generator 623 operates by sensing the voltage drop across
resistor R202 of FIG. 10 using this as an indicator of the amount of
current flowing from inductor 661. Under normal operating conditions
during positive lamp discharge periods the comparator A6 has minimal
effect on the error signal from amplifier A5 at node 819. However during
startup and negative lamp discharge periods the output from comparator A6
operates to limit the swing on error signal node 819 thus reducing the
amount of current pulsed through the modulator. Operational amplifier A5
in general produces an error signal output which fluctuates plus or minus
to 0 volts relative to conductor Q. The output of A5 is dependent upon the
voltage drop across diode 642, the positive lamp discharge switching means
Q103, and resistors 204, all shown in FIG. 10. Transistors 806 and 807
operate in an inverting mode of operation to limit the range of the error
signal at node 819 to .+-.0.7 volts relative to conductor Q. The error
signal is then communicated to integrator circuitry 624.
Integrator circuitry 624 includes operational amplifiers A7 and A8. As
explained above, the output from error signal generator 623 is received at
the noninverting input of operational amplifier A8. The inverting input to
amplifier A8 is connected to the output from operational amplifier A7 via
resistor R268. The inverting input of operational amplifier A8 is also
connected to the output thereof via feedback resistor R270. The inputs to
amplifier A7 include signal Q at the noninverting input via resistor R266.
The inverting input to operational amplifier A7 is connected to the output
thereof via a feedback loop and resistor R267. The inverting input of
amplifier A7 is also connected via resistor R265 to the output of
amplifier A8. The output of operational amplifier A8 is connected to
resistor R271 at the first end thereof. The second end of resistor R271
forms the integrator output and is connected to one side of high frequency
filter capacitor C141. The other side of capacitor C141 is connected to
conductor Q.
FIG. 12A also shows a power supply section 817. Power from the alternating
current line is received through conductor M which is connected to one
side of coupling capacitor C142. The other side of capacitor C142 is
connected to resistor R281. The other end of resistor 281 is connected to
the anode of diode 811 and the cathode of diode 810. The anode of diode
810 is connected to capacitor C152 which has its other side connected to
conductor Q. The anode of diode 810 is also connected to the anode of
zener diode 809 via resistor R280. The alternating current passed across
capacitor C142 is selectively divided with negative charge collecting on
capacitor C152 and positive charge collecting on capacitor C143. Diode 815
and zener diode 809 limit the charge on capacitor C152 to produce the -4.3
volt signal referenced to conductor Q.
The positive charge stored on capacitor C143 is connected to conductor LL
which provides an approximately +17 volt signal with respect to conductor
Q. Resistor R282 is connected between conductor LL and the cathode of
zener diode 812. Capacitor C144 is connected from the cathode of zener
diode 812 across to conductor Q. Zener diode 812 allows an approximately
+12.1 volt signal to be generated on conductor MM. Capacitor C144 serves
to stabilize the voltage generated at that node and on conductor MM. The
anode of zener diode 812 is connected to the first end of resistor R283.
The second end of resistor R283 is connected to the first end of resistor
R284 which has its second end connected to conductor Q. The anode of zener
diode 812 is connected to the anode of diode 813. The cathode of diode 813
is connected to the anode of diode 814 which has its cathode connected to
conductor EE in order to generate the EE signal which is approximately
+0.7 volt with respect to conductor Q. The conductor marked GG
communicates a biasing signal to the base of transistor 821 shown in FIG.
12B. This turns transistor 821 on which draws current from the
approximately +5 volt supply FF through resistors R296 and R297 and
transistor 821 to conductor Q. The node between resistors R296 and R297 is
connected to a comparator 863 which forms a subcircuit within the pulse
width modulator chip 860. The capacitor C147 is connected between the same
input node and conductor Q. Function of transistor 821 is to provide a
soft startup procedure for the pulse width modulator chip so that initial
transient voltage fluctuations occurring during initiation of power to
circuitry 600 does not cause damage within the chip.
FIG. 12B also shows that the integrator output signal on conductor CC is
communicated to the pulse width modulator chip 860 via resistor R294 to a
first error amplifier 861 existing within the pulse width modulator chip.
The noninverting input of error amplifier 861 is connected not only to
resistor R294 but to one end of resistor R293. The opposite end of
resistor R293 is connected to the approximately +5 volt power supply
conductor FF. Conductor FF is also connected to resistor R292 at the first
end thereof. The second end of resistor R292 is connected to the inverting
input of internal error amplifier 861. Resistor R290 is connected between
conductor Q and the inverting input of amplifier 861. The inverting input
of amplifier 861 is also connected to a first end of resistor R291. The
second end of resistor R291 is connected to the output of second error
amplifier 862 and to a first side of capacitor C146. The other side of
capacitor C146 is connected to capacitor C145 which is also connected to a
power pin driving the first error amplifier 861. The opposite side
capacitor C145 is connected to conductor Q.
Pulse width modulator chip 860 functions in the typical manner by receiving
the output signal CC from integrator 624 and processing it through error
amplifier 861 which is communicated to a digital logic section 865 within
the chip. An oscillator 864 within chip 860 provides a triangle wave
function which is advantageously set to 100 KHz as determined by the
values of capacitor C148 and resistor R298 which are connected between
chip 860 and control ground Q.
The pulse width modulator chip internal logic 865 drives internal push-pull
transistors 866 and 867. Transistors 866 and 867 are connected with the
emitters thereof connected to conductor Q. The bases of transistors 866
and 867 are connected to logic unit 865, and the collectors thereof are
connected to pins which conduct output signals from chip 860. The
collector output from transistor 866 is connected to the base of
transistor 832, the cathode of a constant current diode 830, and the
cathode of diode 831. The anode of constant current diode 830 is connected
to the approximately +17 volt supply provided on conductor LL with respect
to conductor Q. Conductor LL is also connected to the collector of
transistor 832 supply driving current thereto which is controllably
conducted from the emitter. Diode 831 is connected with the cathode to the
collector of transistor 866 and the anode to the emitter of transistor
832. Diode 833 is connected with its anode to the emitter and its cathode
to the base of transistor 832. The emitter of transistor 832 is also
connected to one side of a coupling capacitor C150. The other side of
coupling capacitor C150 is connected to the first end of primary coil L30
of a transformer 880. The opposite or second end of coil L30 is connected
to the emitter of transistor 842. The base of transistor 842 is connected
to the collector of the second push pull transistor 867. The constant
current diode 840 is connected with the cathode thereof to the base of
transistor 842 and the anode thereof connected to conductor LL. Diode 841
is connected with the cathode thereof to the collector of transistor 867
and the anode thereof connected to the emitter of transistor 842. Diode
843 is connected with the anode thereof connected to the emitter of
transistor 842 and the cathode connected to conductor LL.
The pulse width modulator chip operates with the push pull transistors 866
and 867 switching at the desired modulation frequency such as 100 KHz.
This causes pulses of current to flow through primary coil L30 which
induce pulses of current in the secondary coil L31 of transformer 880.
Secondary coil L31 is connected with the first end thereof connected to the
anodes of diodes 851 and 852 and the cathode of diode 855. The second end
of coil L31 is connected to the anodes of diodes 853 and 854 and to the
cathode of diode 856. The anodes of diodes 855 and 856 are connected to
conductor II which as shown on FIG. 10 is connected to the source of the
positive modulation transistor 621. The cathodes of diode 851 is connected
to the emitter of PNP transistor 859 and to resistor R299. The opposite
end of resistor R299 is connected to the gate of modulation transistor
621. The collector of transistor 859 is connected to the source of
transistor 621. The base of transistor 859 is connected to the cathodes of
diodes 852 and 854. The base is also connected to the anode constant
current diode 857 which has its cathode connected to the source of
transistor 621. Capacitor C151 is connected between the gate and source of
transistor 621.
The output from integrator circuit 624 is conducted by conductor CC which
is communicated to the pulse width modulator and its associated interface
componentry as shown in FIG. 12B. Conductor FF carries a relatively fixed
5 volt voltage supply relative to conductor Q. This voltage supply passes
through resistor R292 and R290 to conductor Q to generate a relatively
fixed +2.5 volts to the minus input of the operational amplifier 861
within pulse width modulator 860. In a similar fashion the +5 volt voltage
supply connected to conductor FF conducts current through resistor R293
and resistor R295 to conductor Q. This also tends to generate the same
+2.5 volt signal at the plus input of operational amplifier 861 with
respect to the voltage on conductor Q. The integrated signal on conductor
CC passes through resistor R294 to vary the input at the plus terminal of
operational amplifier 861. This causes the output of amplifier 861 to vary
and control the logic section 865 of the pulse width modulator. The logic
section 865 controls the operation of push pull transistors 866 and 867 so
that only one of the transistors is conductive at any particular time.
Operational amplifier 862 is biased into an inoperative condition and
performs no useful function in this circuit. Comparator 863 turns the
logic section 865 on after an appropriate initial start up period is
defined by the soft start circuitry described hereinabove.
When logic circuitry 865 turns first push pull transistor 866 on, it
effectively connects the conductor Q to the base of transistor 832. This
causes transistor 832 to turn off. At the same time transistor 867 is
turned off which allows the regulated current flow through constant
current diode 840 to be applied to the base of transistor 842 which turns
transistor 842 on to conduct current from the +17 volt conductor LL
through transistor 842 to the first coil L30 of transformer 880. The
current path passes through coil L30, capacitor C150 and diode 831 and
down through transistor 866 to conductor Q. The conduction of current
through transistors 842 and 866 produces a relatively negative voltage at
the dot or first end of the secondary coil L31. Accordingly, the second
end of coil L31 is relatively more positive which generates current flow
through diodes 853 and 854. Current flow through diodes 853 and 854 causes
the base and emitter of transistor 859 to be at approximately the same
voltage thus turning transistor 859 off. This allows positive current
through diode 853 to pass through resistor R299 to the gate of transistor
switch 621 thereby turning it on. The constant current diode 857 maintains
the source of transistor 621 at a diode drop lower voltage than the gate
thus assuring conduction through transistor 621 when a pulse is received.
In the opposite situation when second push pull transistor 867 is
conductive, this causes transistor 842 to be turned off. When transistor
867 is turned on, then transistor 866 is turned off according to the logic
of 865. When transistor 866 turns off, it causes the base of transistor
832 to rise in voltage towards conductor LL at +17 volts thus turning
transistor 832 on to conduct positive current from conductor LL which is
capacitively coupled across the capacitor C150 to generate a relatively
more positive voltage at the first or dotted end of primary coil L30 which
in turn induces a relatively positive voltage at the first or dotted end
of secondary coil L31.
The gate of transistor 621 is forwardly biased with respect to the source
when current is conducted either through push pull transistors 866 or 867.
When the push pull transistors switch, there is a drop in current through
coil L30. The charge stored on capacitor C151 thus discharges through
resistor R299 and raises the emitter of transistor 859 higher in voltage
than the base which is discharged through the constant current diode 857.
This causes transistor 859 to turn on which causes the gate and source to
be connected together thus turning the modulator transistor 621 off.
Power is modulated by transistor 621 by controlling the duty cycle during
which transistors 866 and 867 are both off, thus increasing or decreasing
the current with decreasing or increasing off time, respectively, per
cycle of the push-pull transistors 866 and 867.
The negative modulator drive circuitry 632 is shown in FIGS. 13A and 13B.
In general the circuitry construction is the same as that shown in FIGS.
12A and B and as described above, except with respect to certain polarity
changes which will be described below and the fact that the inputs and
outputs from the circuit are connected into the general electronic ballast
circuit 600 with respect to the negative channel rather than to the
positive channel. The inputs to the negative error signal generator is via
conductor U which generates a -4 volt supply relative to the lamp supply
terminal 700a. Diode 901 is used in lieu of diode 801 with diode 901
connected with the cathode thereof connected to conductor U and the anode
thereof connected between resistors R251' and R252'. Resistor R252' has
its opposite end connected to the plus input of operational amplifier A5'.
Resistor R253' is connected from the plus input of operational amplifier
A5' to the conductor R. Diodes 902 and 903 are connected in parallel
between the plus input of operational amplifier A5' and conductor R in
opposite orientation. Feedback resistor R254' is connected from the output
of amplifier A5' to the plus input.
Conductors R and S are connected at opposite ends of the negative current
sense resistor R203 shown in FIG. 10. Conductor S is connected to the
minus input of operational amplifier A6' using input resistor R259'. The
plus input of operational amplifier A6' is connected to conductor R via
input resistor R258'.
Remaining portions of negative modulator drive circuit 632 are the same as
described above with respect to positive modulator drive circuitry 622
with the added prime to indicate usage in the negative channel. The
outputs from the pulse width modulator chip 860' and its coupling
circuitry result in signals on conductors JJ and KK which are connected to
the gate and source of negative modulating transistor 631, respectively.
The operation of negative modulating drive circuitry is substantially the
same as described above with respect to the positive modulating drive
circuitry 622 with proper consideration given to the opposite polarity.
Table VI below presents preferred values of resistance, inductance and
capacitance for resistors, inductors and capacitors useful in a preferred
form of circuit 600.
TABLE VI
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RESISTORS
R200, R201 150K ohms
R202, R203 0.1 ohms
R204A, B 0.47 ohms
R205A, B 0.47 ohms
R206, R207 470K ohms
R210 82 ohms
R211 2.2K ohms
R212 680 ohms
R213 20 ohms
R214 3.3K ohms
R215 10K ohms
R216 220 ohms
R217 3.3K ohms
R218 270 ohms
R219 220 ohms
R220 82 ohms
R221 2.2K ohms
R222 680 ohms
R223 20 ohms
R224 3.3K ohms
R225 10K ohms
R226 220 ohms
R227 3.3K ohms
R228 270 ohms
R229 220 ohms
R250, R250' 1.5M ohms
R251, R251' 1.5M ohms
R252, R252' 150K ohms
R253, R253' 47K ohms
R254, R254' 560K ohms
R255, R255' 47K ohms
R256, R256' 12K ohms
R257, R257' 13K ohms
R258, R258' 10K ohms
R259, R259' 10K ohms
R260, R260' 330K ohms
R261, R261' 3.6M ohms
R262, R262' 3.3K ohms
R263, R263' 2.2K ohms
R264, R264' 3.3K ohms
R265, R265' 470K ohms
R266, R266' 240K ohms
R267, R267' 470K ohms
R268, R268' 470K ohms
R269, R269' 240K ohms
R270, R270' 470K ohms
R271, R271' 18K ohms
R280, R280' 68 ohms
R281, R281' 33 ohms
R282, R282' 330 ohms
R283, R283' 1.6K ohms
R284, R284' 1.6K ohms
R290, R290' 100K ohms
R291, R291' 47K ohms
R292, R292' 100K ohms
R293, R293' 100K ohms
R294, R294' 47K ohms
R295, R295' 100K ohms
R296, R296' 33K ohms
R297, R297' 10K ohms
R298, R298' 33K ohms
R299, R299' 33 ohms
CAPACITORS
C100, C101 560 microfarads
C102, C103 3 microfarads
C104, C105 0.02 microfarads
C108, C109 5 microfarads
C120, C130 220 microfarads
C121, C131 100 microfarads
C122, C132 0.47 microfarads
C123 47 microfarads
C124 47 microfarads
C140, C140' 0.02 microfarads
C141, C141' 0.1 microfarads
C142, C142' 1 microfarads
C143, C143' 330 microfarads
C144, C144' 47 microfarads
C145, C145' 0.1 microfarads
C146, C146' 0.01 microfarads
C147, C147' 0.47 microfarads
C148, C148' 220 picofarads
C149, C149' 0.47 microfarads
C150, C150' 0.1 microfarads
C151, C151' 0.002 microfarads
INDUCTORS
661, 662 700 microhenries
______________________________________
In compliance with the statute, the invention has been described in
language more or less specific as to structural features. It is to be
understood, however, that the invention is not limited to the specific
features shown, since the means and construction herein disclosed comprise
a preferred form of putting the invention into effect. The invention is,
therefore, claimed in any of its forms or modifications within the proper
scope of the appended claims, appropriately interpreted in accordance with
the doctrine of equivalents.
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